September 23, 2022

Kenya certificate of Secondary Education 2016 Physics paper 1 SECTION A: (25 marks) Answer all the questions in this section in the spaces provided 1. State what mechanics as a branch of physics deals with. (1 mark) 2. Figure 1 shows a change in volume of water in a measuring cylinder when an irregular solid is immersed in it. Given that the mass of the solid is 567 g, determine the density of the solid in g/cm3 (Give your answers correct to 2 decimal places). (3 marks) 3. When a drop of an organic acid of known volume is dropped on the surface of water in a large trough, it spreads to form a large circular patch, State one assumption made when the size of the molecule of the acid is estimated by determining the area of the patch. (I mark) 4. Figure 2(a) and 2(b) show capillary tubes inserted in water and mercury respectively. Water It is observed that in water the meniscus in the capillary tube is higher than the meniscus in the beaker, while in mercury the meniscus in the capillary tube is lower than the meniscus in the beaker. Explain these observations. (3 marks) 5. Figure 3 shows a hot water bath with metal rods inserted through one of its ends. Some candle wax is fixed at the end of each rod. Use this information to answer questions 5(a) and 5(b). (a) What property of metals could be tested using this set-up? (1 mark) (b) Besides the length of the rods that is kept constant, what else should be kept constant when comparing the property for the different metal rods? (1 mark ) 6. Figure 4 shows a uniform light bar resting horizontally on corks floating on water in two beakers A and B. Explain why the bar tilts towards side A when equal amount of heat is supplied to each beaker (2 mark) 7. Figure 5 shows an aluminium tube tightly stuck in a steel tube. Explain how the two tubes can be separated by applying a temperature change at the junction given that aluminium expands more than steel for the same temperature rise. (2 marks) 8. (a) An aeroplane is moving horizontally through still air at a uniform speed. It is observed that when the speed of the plane is increased, its height above the ground increases. State the reasons for this observation. (1 mark) (b) Figure 6 shows parts A, B and C of a glass tube. State with a reason the part of the tube in which the pressure will be lowest when air is blown through the tube from A towards C. (2 marks) 9. The three springs shown in Figure 7 arc identical and have negligible weight. The extension produced on the system of springs is 20cm Determine the spring constant of each spring. (2 marks) 10. Figure 8 shows two cylinders of different cross-sectional areas connected with a tube. The cylinders contain an incompressible fluid and are fitted with pistons of cross-sectional areas 4 cm2 and 24 cm2. Opposing forces P and Q are applied to the pistons such that the pistons do not move. If the pressure on the smaller piston is 5N/cm2, determine force Q. (2 marks) 11. Figure 9 shows a uniform cardboard in the shape of a parallelogram. Locate the centre of gravity of the cardboard. (1 mark) 12. State why it is easier to separate water into drops than to separate a solid into smaller pieces. 13. The graph in Figure 10 shows the velocity of a car in the first 8 seconds as it accelerates from rest along a straight line. > Determine the distance travelled 3.0 seconds after the start. (2 marks) SECTION B: (55 marks) Answer all the questions in this section in the spaces provided. 14. (a) Explain why it is advisable to use a pressure cooker for cooking at high altitudes. (2 marks) (b) Water of mass 3.0 Kg at 20°C is heated in an electric kettle rated 3.0KW. The water is heated until it boils at 100°C. Given that the specific heat capacity of water = 4200J Kg-1 K-‘, heat capacity of the kettle = 450.1K-1, specific latent heat of vaporisation of water = 2.3 M.T Kg-1. Determine: (i) the heat absorbed by the water. (3 marks) (ii) heat absorbed by the electric kettle. (2 marks) (iii) the time taken for the water to boil. (3 marks) (iv) how much longer it will take to boil away all the water. (3 marks) 15. (a) State the meaning of the term ideal gas. (1 mark) (b) The pressure acting on a gas in a cylinder was changed steadily while the temperature of the gas was maintained constant. The value of volume V of the gas was measured for various values of pressure. The graph in Figure 11 shows the relation between the pressure P, and the reciprocal of volume, Vv. (i) Suggest how the temperature of the gas could be kept constant. (2 marks) (ii) Given that the relation between the pressure P1 and the volume, V1 of the gas is given by Pv = K, where K is a constant, use the graph to determine the value of K. (4 marks) (iii) What physical quantity does K represent? (1 mark) (iv) State one precaution you would take when performing such an experiment. (1 mark) (c) A gas occupies a volume of 4000 litres at a temperature of 37°C and normal atmospheric pressure. Determine the new volume of the gas if it is heated at constant pressure to a temperature of 67°C (Normal atmospheric pressure, P = 1.01 X 105 Pa). (4 marks) 16. (a) Define the term velocity ratio of a machine. (1 mark) (b) Figure 12 shows part of a hydraulic press. The Plunger is the piston where effort is applied while the Ram piston is the position where the load is applied. The Plunger has cross-section area a m2 while the Ram piston has cross-section, A m2. When the Plunger

Questions and Answers 2017 Physics paper 2 SECTION A: (25 marks) Answer all the questions in this section in the spaces provided 1. State any two uses of microwaves. (2 marks) – Cooking/warming/heating – Communication / Radar/ measure distances 2. In a laboratory there are four metals — tin, nickel, copper and cobalt. Of these metals, name the metals that are; (a) magnetic, (1 mark) – Nickel, cobalt (b) non-magnetic. (1 mark) – Tin, copper 3. State one use of echoes. – Measuring distances/ speed of sound Define polarization (1 mark) – Polarization is the formation of hydrogen gas at the positive terminal of the cell. 5. State two advantages of using convex mirrors to monitor movements in a large supermarket. (2 marks) – Have a wide/wider field of view. – Form upright images. 6. Figure 1 shows an insulated wire wound on a U-shaped iron core connected to a battery. Determine the polarity of A. (1 mark) – A South pole 7. Explain how the greenhouse gets warm. (2 marks) – The light passes through the walls and gets absorbed by the soil, emitting energy of longer wavelengths which cannot penetrate the walls hence get trapped within the green house causing heating. 8. Draw a circuit diagram to show a p-n junction diode in the forward biased mode. (1 mark) 9. Figure 2 shows a virtual image I formed by a convex lens. Draw a ray diagram to locate the object. (3 marks) 10. Write an equation to show how an element zX decay to element Y by emitting a beta particle. (1 mark)   11. Explain what is observed when an uncharged sphere is brought close to a positively charged electroscope. (3 marks) – The leaf falls -Charge is induced on the sphere causing repulsion of electrons to the leaf hence leaf falls. 12. Figure 3 shows a transverse wave Determine the frequency of the wave. (2 marks) T= 20 s f=1/2 =1/20 = 0.05 Hz 13. Figure 4 shows three resistors connected in series. Using Ohm’s law, show that the effective resistance is given by the expression: RT= RI + R2 + R3 (3 marks)   14. State how heating is achieved in a resistance wire. (1 mark) Conversion of the Kinetic energy of the electrons into heat energy/ conversion of electrical energy to heat energy SECTION B: (55 marks) Answer all the questions in this section in the spaces provided. 15. (a) Figure 5 shows the interface between glass and air. Draw on the figure a ray diagram to illustrate the critical angle. (3 marks) (b) Figure 6 shows a ray of light incident at right angles to face AB of a right angled glass prism of refractive index 1.62. Figure 6 (i) Determine the critical angle of the material. (3 marks) (ii) Complete the ray diagram to show the path of light until it leaves the prism. (2 marks) (c) State any two applications of prisms. (2 marks) – Dispersion of white light – In periscopes – In Binoculars – In telescopes 16. (a) Figure 7 shows a set up that may be used to observe photoelectric effect. A radiation is incident on the cathode. It is observed that the microammeter registers a current. (i) Explain how the current is produced. (2 marks) – . Radiations cause photo electrons to be ejected from the metal surface (cathode), the electrons are attracted by the anode hence current flows. (ii) State with a reason what must be done for a higher current to be registered. (2 marks) – . use a radiation of higher intensity Source is made moved closer/ increase anode voltage/accelerating voltage. (iii) It was observed that for a certain incident radiation, no current was registered. Explain this observation. (2 marks) The frequency of the incident radiation is below the threshold frequency of the surface hence no emission can take place (b) A monochromatic light of wavelength 4.50 x 10′ m is incident on a metal surface of threshold frequency 5.5 x 10″ Hz. (Speed of light c is 3.0 X 1O’ ms-‘ and planks constant h is 6.63 x 10-34Js). Determine (i) the work function of the metal surface, (3 marks) (ii) average kinetic energy of the emittal photoelectrons. (4 marks) 17. (a) Figure 8 shows a conductor AB connected to a galvanometer and placed between two permanent magnets. Conductor AB is moved perpendicular to the magnetic field. State and explain the observation made on the galvanometer. (3 marks) – A momentary deflection is observed, Conductor cuts the field. An emf is induced in AB Causing current in the circuit (ii) State the effect of moving the conductor faster. (1 mark) – A bigger deflection is observed/ higher current (b) A transformer is used to step down 240V to 12V for use in an electric appliance operating at 0.5A. If the primary coil has 600 turns, determine the; (i) number of turns in the secondary coil, (3 marks) 18. (a) State two factors that affect the capacitance of a parallel plate capacitor. (2 marks) – Area of overlap of the plates – Distance between the plates. – Type of dielectric. (b) Figure 9 shows an electric circuit in which three capacitors are connected across a power supply. (2 marks) (i) total capacitance, (4 marks) (ii) Quantity of change stored on the 8uf capacitor(3 marks) 19. (a) Figure 10 shows a block diagram of a cathode ray oscilloscope (CRO). (i) State the names of the parts labelled B1 and B2 (2 marks) B1 – y detecting plates B2 -X deflecting plates (ii) State and explain the function of the part marked A. (3 marks) Grid; controls the intensity by controlling the number of electrons reaching the screen. If made more negative less electrons pass through. (b) Figure 11 shows a trace of a signal observed on the screen of a CRO. The time-base setting is 20 mscm-‘. Determine the frequency of the signal. (4 marks) T= 8 X 20 ms-1 = 160 = 0.16 s F

2017 Physics paper 1 SECTION A: (25 marks) Answer all the questions in this section in the spaces provided. 1. In order to determine the size of an oil molecule, a student performed an experiment using five oil drops to make a circular patch of the oil on the surface of water in a water bath. State two assumptions made by the student during the calculations. (2 marks) – The patch was monolayer. – The patch was a perfect cylinder. – Molecular diameter is uniform. – The patch is a perfect circle. 2. In an experiment to determine the density of Liquid R. a student obtained the followed data: Mass of an empty density bottle = 55.0 g — Mass of the density bottle + water = 80.0 g — Mass of the density bottle + Liquid R = 70.0 g Determine the density of Liquid R. (density of water is 1000 kgm (3 marks) 3. It is observed that when 20 cm’ of alcohol is mixed with 20 cm’ of water, the volume of the mixture is 39 cm’. State a reason why the volume of the mixture is not 40 cm’. (1 mark – Spaces between the water molecules are occupied by the alcohol molecules. 4. When a liquid is heated in a glass flask, it is observed that the level at first goes down and then rises. Explain this observation. (2 marks) – The flask expands first before ✓ the liquid. Then the liquid expands more. 5. Figure 1 shows a uniform wooden bar at equilibrium with two cans Y and Z of equal mass but different diameters. The cans are simultaneously filled with equal volumes of water. Explain the observation made. (2 marks) – The wooden bar remains in equilibrium. the weight remains the same on both sides. Hence turning effect is the same✓ to the edge causing a bigger turning effect (moments) 6. State the reason why the speed of water at the narrow section of a river is higher than at the wider section. (1 mark) – To conserve mass — (A1 V1 = A2V2) / ensure the volume flux is constant. 7. .A stone is thrown .vertically upwards. Sketch a graph of potential energy (y axis) against time as the stone moves until it hits the ground. (1 mark) 8. Using the definition of impulsive force. show that F = ma (3 marks) 9. Figure 2 shows a round bottomed flask fitted with a long capillary tube containing a drop of coloured water. The flask is immersed in ice water for sometime. State the observation made. (2 marks) – The drop first rises” then falls 10. State one assumption for the experiments carried out to verify the gas laws. (1 mark) – The gas is ideal gas 11. A student who wanted to take a bath mixed 4 kg of water at 80 °C with 6 kg of water at 20 °C. Determine the final temperature of the water. (3 marks) 12. A uniform metre rule is pivoted at its centre. Two weights of 20N and 10 N are suspended at the 20cm and 100cm marks respectively. Determine the position at which a 10N weight should be suspended in order to balance the system. (3 marks) 13. Figure 3 shows two possible designs of a three legged stool. (b) State with a reason what would be observed on the spacing between the dots on the tape when the trolley is made to move on a horizontal surface. (2 marks) – The spacing reducing with time – The troley decelerates with time on a horizontal surface 15. (a) A student was provided with several identical masses, a metre rule, a spring and a stand, boss and clamp. Outline five steps that the student should follow in order to verify Hooke’s law. (5 marks) – Hung the spring on the stand and note the position of the pointer using the metre rule. – Suspend a mass on the spring and note the new position of the pointer. – Increase the load in steps and record the position of the pointer for each load. – Draw a table of weight against extension. – Plot a graph of force against extension. (b) Figure 4 shows a graph that was drawn from the results obtained in an experiment to study the extension of a spring. From the graph determine: (i) The spring constant K. (3 marks) (ii) The load that causes an extension of 3 x 10′ m. (1 mark) – Load = 0.38N (c) Three identical springs of spring constant 100 Nm ‘ are arranged as shown in Figure 5 to support a 5N load. Determine the total extension for the arrangement 16. (a) In an experiment to determine the size of an oil molecule, oil is placed on the surface of water after sprinkling lycopodium powder on it. (i) State two reasons why oil is used. (2 marks) – Oil doesn’t mix with water. – Oil is less dense hence floats on the water surface. (ii) State the function of the lycopodium powder. (1 mark) – To show boundary of the oil patch clearly, for measurements to be taken. (iii) State any two assumptions that are made in this experiment. (2 marks) – The oil drops is a perfect sphere. – The patch is monolayer. – The patch is a perfect circle. – Molecular diameter is uniform. (iv) Explain why the oil spreads on the surface of water. (2 marks) – The oil breaks the surface tension ✓ making the patch to form a perfect circle. (b) The following data was obtained from an experiment to determine the size of a palm oil molecule. — Volume of 100 drops of palm oil = 15.0mm3 — Area of a patch from one drop of oil = 8.0 X l04mm2 Determine the size of a palm oil molecule. (3 marks)   17. (a) State the law of flotation. (1 mark) – A floating body displaces its own weight of

2018 Physics paper 3 Question 1 You are provided with the following:   Some water in a container A 10 ml measuring cylinder A piece of a glass rod A 10 g mass 5 paper clips A half metre rule A metre rule Two stands, two bosses and two clamps Three pieces of sewing threadProceed as follows: (a) Pour 6 ml of the water into the measuring cylinder. Lower the glass rod into the water and determine the volume V of the glass rod. V=3.4 cmcm3± 0.2(1 mark) Remove the glass rod from water. (b) Using a stand and a piece of string, suspend the half metre rule at its centre of gravity C so that it balances horizontally with the scale facing you. C = 25.3 cm ± 0.1 Using a second stand, clamp a metre rule vertically near one end of the half metre rule to note the height at which the half metre rule is horizontal. Maintain this height throughout the experiment Record the centimetre mark of the centre of gravity C. CX = 2.2 cm ± 0.1 cm(1 mark) (c) Using the string, suspend the 10 g mass on the half metre rule at a distance d = 2 cm from C. The distance d = 2 cm should be maintained throughout the experiment. Balance the half metre rule by suspending the glass rod using a string at a distance X from C. Record the value of X X=…………………….cm(1 mark) (d) Using the results in part (a) and (c) determine the; (i) mass of the glass rod, (2 marks) 10 x 2 = mx 2.2 M =m/v 10 x 2/2.2 = 9.1g ± 1 (ii) density of the glass rod. (2 marks) ƿ =m/ v 9.1/3.4 =2.68 gcm -3 (e) Remove the glass rod. Push the half metre rule through one paper clip and adjust the position of the clip to a point P where the half metre rule balances horizontally. See Figure 1. (f) Record the centimetre mark for point P in Table 1.(g) Repeat part (f) for the other number of clips shown in Table 1 and complete (the clips may be suspended by connecting them us a chain of the required number) (4 marks) x (h) Plot a graph of l/L(y axis) against the number of clips N.(4 marks) (i) Determine the slope S of the graph.(3 marks) (j) Determine K given that 1/L = 0.05 KN(2 marks) Question 2You are provided with the following: (i) A voltmeter (ii) A resistor labelled 10 1 (iii) A resistance wire mounted on a half metre rule labelled X (iv) Two cells in a cell holder (v) A switch (vi) Eight connecting wires (vii) A micrometer screw gauge (viii) A resistor labelled 10 KB (ix) A galvanometer (x) A beaker containing a liquid labelled L (xi) Two copper plates (xii) A resistance wire labelled AB and mounted on a millimetre scale (xiii) A jockey (xiv) A vernier calliper Proceed as follows: Part A (a) Measure and record the diameter d of the resistance wire x d=0.36mm۪.005 3.6X10-4M (b) Set up the circuit as shown in Figure 2. (i) Close the switch and record the potential difference V across the 10a resistor. (1 mark)V1= 1.7 V ± 0.2 (ii) Open the switch. Determine the current I flowing in the circuit.(2 marks) R=V/1 =1/0.17 =5.88 ☊ (c) (i) Now connect the voltmeter across wire X. Close the switch and record the potential difference V2 across wire X. V2=1.0v۪.2 (ii) Determine the resistance R of wire X.(2 marks) v1K=5.88/0.5 11.76☊m-1 (iii) Determine K the resistance per metre of wire X.(1 marks) (iv) Determine Q given that Q = n Kd2/4 (where d is in metres).(1 marks) Part B (d) (i) Using the vernier callipers measure and record the width W of one of the copper plates W =5.0cm± 0.10 (ii) Determine the area A of a 5 cm length of the copper plate A =5X50 cm2 =25.00cm2 (e) Using stands and clamps, hold the copper plates in the beaker such that both plates: (i) reach the bottom of the beaker; (ii) are parallel, vertical and facing each other; (iii) are separated from each other by a distance S. (f) Connect the copper plates to the circuit as shown in Figure 3. (g) Set the separation distance between the copper plates S to 3 cm. Using the jockey tap wire AB at various points to obtain a point P at which the galvanometer does not show any deflection. Record the balance length L (from A to P) in Table 2.(h) Repeat part (g) for other values of S shown in Table 2 and complete the table. (6 marks) (i) Determine the average value of Z. (2 marks) Z average = 325.73+295.43+315.63/3

Questions and Answers 2017 Physics paper 2 1. Explain why the walls of a studio are padded with woolen materials.(2 marks)   Sounds produced in the studio are reflected by the walls producing echoes in the room; that interfere with the signals transmitted. The woolen materials will absorb the sound hence reduce the echo effects.2. State one characteristic of soft X-rays that distinguish them from hard X-rays.(1 marks)   Hard x-rays have a higher frequency than soft x-ray. Hard x-rays have more penetrating power than soft x-rays.3. Figure 1 shows a bar magnet AB suspended by a string. When the North pole of another magnet is brought close to end A, there is repulsion. State the polarity of end B. (1 mark) End B is a south pole. 4. State what happens to the image formed by a pin hole camera when the size of the hole is increased. (1 mark) The image is blurred. 5. The angle of incident for a ray of light moving from air to a certain liquid is 30°. Given that the refractive index of the liquid is 1.36, determine the angle of refraction. (2 marks) Sin i = q Sin r Sin30/sinx = 1.36 Sin30/i.36 = Sin x x = 21.6° 6. An electric kettle is rated 1.8 kW, 240 V. Determine the rating of the fuse that may be used in the kettle. (3 marks) I = p/v 180/240 = 7.5A Fuse rating of 8A is suitable. 7. Figure 2 shows the image of an object O placed on the principle axis of a convex mirror. On the figure, draw a ray diagram to locate the object. (3 marks) 8. Define radioactivity.(1 mark) Spontaneous disintegration of atomic nuclei by emission of radiations. 9. A transformer has 600 turns in the primary coil and 9000 tums in the secondary coil. If the transformer is 100% efficient and the current in the secondary coil is 0.15A, determine the current in the primary coil. (3 marks) 10. The sharp point of a pin is brought near the cap of a positively charged electroscope. State and explain the observation made on the leaf of the electroscope. (3 marks)The leaf collapses — Negative charge is induced on the tip of the pin. Pin repels negatively charged fair ions which discharges the electroscope). 11. Arrange the following radiations in the order of increasing wavelengths; Purple light, Gamma rays, infrared and ultraviolet.(1 marks)   Gamma, ultraviolet, purple light, infrared.12. State the purpose of manganese (IV) oxide in a dry cell.(1 mark)   It acts as a depolarizer.13. State the meaning of the term battery.(1 mark) A battery is a group of cells connected in series or parallel. 14. Figure 3 shows two current-carrying wires A and B passing through a cardboard. On the diagram, sketch the magnetic field lines around the wires to show how the fields interact.(2 marks) Field around each wire attraction.SECTION B (55 marks) Answer all the questions in this section in the spaces provide. 15. (a) Electrical energy is transmitted at very high voltages and low current. (i) Describe how the high voltages are attained. (1 mark) (i) By use of step-up transformers low input voltages are stepped up to high voltages for transmission. (ii) State two reasons why thick aluminium wires are preferred to copper wires for transmission over long distances. (2 marks)   They are cheaper They are lighter / lower density / lower weight(b) Figure 4 shows an electric cooker connected to the mains supply. X, Y and Z are the mains wires.   State with a reason the name of wire Y. (2 marks)  Y is the earth wired, it is connected to the casing of the cooker.(c) A student has some coloured bulbs rated 60 W, 240 V to be connected for decorations. (i) State the number of such bulbs that can be connected normally to a 240V supply through a 5 A fuse. (2 marks) I = P/v 60/240 = 0.25A No. of bulbs = 20/0.25 =20 (ii) If the cost of electric energy is Ksh 3.00 per kWh, determine the cost of running the bulbs in (c) (i) for 5 hours daily for 20 days. (3 marks) Cost = Power x time x rate) 60/1000 X 20 x 5 x 20 x 3 = ksh. 360.00 16. (a) State the meaning of the following terms: (i) Photoelectric effect(1 marks) The emission of electrons from a metal surface when light/ electromagnetic radiations shine on it. (ii) Threshold frequency(1 marks) The minimum frequency of radiation required to eject electrons from a metal surface. (b) Figure 5 shows some light incident on the cathode of a photocell. The photocell is connected in series with a battery, a variable resistor and a microammeter.   (i) Explain how the microammeter reading is affected when the intensity of the incident light is increased. (2 marks) Increased intensity increases the number of electrons emitted( hence a higher current reading on the microammeter. (ii) State the reason why the tube is evacuated. (1 mark) To minimize collisions between electrons and air molecules which would cause loss of energy. From the graph, determine: (i) Plank’s constant h, (3 marks) (ii) the threshold wavelength k, given that the speed of light C is 3.0 X 10’ms°’. (3 marks) 17. (a) Water waves from a certain source move from the shallow end to the deep end. State the change that occurs at the deep end on the following:(i) Frequency(1 marks)   No change in frequency(ii) Wavelength(1 marks) Wavelength increases (iii) Velocity(1 marks)   Velocity increases(b) (i) A biconvex lens forms an upright image twice the size of the object. If the focal length of the lens is 20 cm, determine the object distance. (4 marks) Image is virtual hence magnification = —2 (ii) State two optical instruments which produce a magnified real image using a convex lens. (2 marks)  A film projector A compound microscope(c) State one difference between the working of the human eye and the lens of

2018 Physics paper 1 Section A: (25 marks) 1. State the reason why an object on earth has a higher weight than on the moon. (1 mark) Earth’s gravity is higher than the moon’s gravity 2. Figure 1 shows the position of a students cye while illustrate the length of a wooden block using a theme rule. Determine the 1cngth of’the block as viewcd by the student. (1 mark) 7.3 —6.0 = 1.3cm 3. Describe how the knowledge of the oil drop experiment may be used to estimate the area of oil spillage from a ship in the sea assuming the sum face water is not distort bed. (3 marks)   Using the same oil spilled, to measure a known volume. Determine the area of spread of the measured volume (on the same water (sample). Estimate the area of spread on the sea.4. Figure 2 shows an instrument used to measure atmospheric pressure.   (a) State with a reason the modification that would be required in a similar set up if mercury were to be replaced with water. (2 marks) The tube will be very long since water has much lower density than mercury 5. It is observed that a drop of milk carefully put into a cup of water tums the water white after some time. State the reason for this observation. (1 mark) Milk particles move to occupy the spaces between the water particles through diffusion. 6. Figure 3 shows the shape of a bimetallic strip after it was cooled below room temperature. Explain why the strip curved is as shown. (2 marks ) Brass contracts more than invar hence contracts leaving the side with invar longer hence the curve. 7. A wooden cube of side 0.5m floats in water frilly submerged. Determine the weight of’the cube.density of the water = 1gm-3).(2 marks) Volume of water displaced = 0.5 x 0.5 x 0.5 = 0. l25m3 W of cube. — weight of water displaced (a floating body) = lx 125000g = l25kg = 1.25 x 103N 8. Figure 4 shows a stonc whirled in a veitical circle. On the axes provided, sketch a graph of tension against time as the stone moves through point A, B, C and D. (3 marks) (a) On the diagram, sketch the path followed by the ball as it moves.(1 mark) (b) Explain why the ball takes that path.(3 mark) Because of Bemoullis effect caused by diference in air pressure due to the streamlines. As the ball moves to the right airstreams move to the left . Spin is anti-clockwise, a region of low pressure forms above lifting the ball. 10. Figure 6 shows the relationship between volume and pressure for a certain gas. Name the law that the gas obeys (1 mark) Boyles law 11. Figure 7 shows an L-shaped wooden structure. On the diagram construct appropriate lines to show the position of’ the centre of gravity for the structrne. (2 marks) 12. Figure 8 shows the graph of extension against force for a certain helical spring. On the same diagram sketch the graph of extension against force for a spring with a lower value of spring constant. (1 mark) 13. State two ways in which a mercury based thermometer can be modified to read very small temperature changes. (2 marks)   Making the bulb thinner. Making the bore narrower.SECTION B (55 marks) 14. (a) State two differences between boiling and evaporation.(2 marks)   Boiling takes place at fixed temperature while evaporation takes at all temperatures. Boiling takes place in the entire liquid while evaporation takes place at the surface.(b) State three ways in which loss of heat by conduction is minimised in a vacuum flask. (3 marks)   Presence of a vacuum. Poor conductor material used to make stopper. Use of glass (poor conductor).(c) In a certain experiment, 50 g of dry steam at 100°C was directed into some crushed ice at 0 °C. (Latent heat ofvoporisation of water is 2.26 X 106 Jkg-I. latent heat of;fusion fi)r ice is 3.34 X 105 Jkg-/ and specific heat capacity of water is 4.2 X 103 Jkg-‘) Determine the: (i) quantity of heat lost by steam to change to water at 100 °C.(2 marks) Heat lost by steam at 100°C. MLv =5.0 x 10-2×2.26×106 = 11.3 x 104 1.13 x 105J (ii) quantity of heat lost by water to cool to 0°C.(2 marks) Heat lost by hot water to cool to 0°C. MCAθ = 5.0 x 10-2 x 4.2 x 103 x 102 = 2.1x 104J (iii) mass of ice melted at 0 °C.(2 marks) Amount of ice melted at 0°C. MiceLf = Mlv+MCA8 M= 2.1x 104 +1.13 x105/ 3.34 x 105 = 0.401kg. — 401g 15. (a) State Newton’s fiist law’ of motion. (1 mark)   A body remains in its state of rest or uniform motion in a straight Line unless acted upon by an external force.(b) A wooden block resting on a horizontal bench is given an initial velocity u so that it slides on the bench for a distance x before it stops. Various values of x are measured for different alnes of’tlie initial velocity. Figure 9 shows a graph of u<sup2< sup=””> against x.</sup2<> (i) Determine the slope S of the graph. (3 marks)(i) Slope = ∆U2/∆x = 50 — 0/8-0 6.25 (ii) Determine the value of k given that u2 = 20kd where k is a frictional constant for the sui tacc. (2 marks) (ii) U2/x = 20k butU2/x= slope K=slope/20 6.25/20 K = 0.3125 (iii) State with a reason what happens to the value of k when the roughness of the bench surface is reduced. (2 marks)   K would reduce since friction has reduced(c) An object is thrown vertically upwards with an initial velocity of 30 ms ‘. Determine its maximum height (acceleration due to gravity g is 10 mw’). (3 marks) Hmax =u2/2g =30 x 30/2 x 10 90/2 = 45m 16. (a) An electie crane uses 8.0 x 10‘ N of energy to lift a load of 2.0 X 104 N

Questions and Answers 2019 Physics paper 2 1. Figure 1 shows two plane mirrors inclined at an angle of 120° to each other. A ray of light makes an angle or 40° with the first mirror. By completing the ray diagram determine the angle of reflection on the second mirror. (2 marks) Correct reflections at the two mirrors. Angle of reflection = 70°2. State the reason why an increase in leaf divergence is the only sure way of determining whether an object is negatively charged using a negatively charged electroscope. (l mark)   An uncharged conductor will also cause a decrease on the divergence of the leaf. OR  Both positively charged conductor and an uncharged body cause a de- crease in divergence.3. State two properties of magnetic field lines around a bar magnet. (2 marks)   Do not cross one another. They are complete loops. Direction of field is from North to South. They are normal to the surface at the poles. Closer at the poles and further apart away from the poles.4. Figure 2 shows an incomplete circuit for an electromagnet. (a) Complete the diagram to show how a battery should be connected at A so that the polarities at P and Q are South and North respectively. (1 mark) (b) State two ways in which the strength of the electromagnet in (a) can be increased. (2 marks)   Increasing the number of turns in the coil. the current (or number of cells).5. In a siren, sound is produced when a jet of air is directed perpendicular to a ring of holes on a rotating wheel. Explain the effect on the pitch of sound produced when the speed of rotation of the wheel is increased. (2 marks)   Increasing speed increases the frequency of the sound causing an increase in the pitch (higher pitch).6. State the reason why the current produced by a simple cell falls rapidly when the cell is being used. (1 mark)   Polarization occurs.7. Figure 3 shows a cell connected in series with an ammeter, a 2 resistor and a switch. A volumeter is connected across the cell With the switch open, the voltmeter reads 1.5 V. Given that the internal resistance of the cell is 0.5 II, determine the ammeter reading when the switch is closed. (3 marks)I=V/R = 1.5 /2 + 0.5 = — 0.6A 8. State two uses of gamma rays in medicine. (2 marks)   To sterilize medical equipment To kill cancerous cells and malignant growths in the body.9. Figure 4 shows the input and output signals on a CRO screen when two diodes are used during a full wave rectification. Explain how the two diodes rectify the input signal. (3 marks)  During the first half cycle of the input signal, current flows in the first diode, During the second half cycle of the input signal, current flows in the sec- ond diode, When the currents through the two diodes are combined a fully rectified wave signal is obtained as the output signal.10. State how the intensity of X-rays in an X-ray tube can be increased. (3 marks)   By increasing the heating current in order to produce more electrons. Increasing the filaments current. Increasing the temperature of the cathode11. Figure 5 shows part of the lighting circuit in a house. State two errors in the wiring circuit. (2 marks)  Fuse in the neutral wire instead of the live wire. Switch to lamp on the neutral Swire instead of live wire. Connection of lamp B on Live wires only.12. Uranium decays as shown below. Name the particle X that is emitted during this decay. (1 mark)  Alpha particle.13. State the disadvantage of rising a convex mirror as a driving mirror. (1 mark)   Shows the object as being further than it actually is. Shows diminished images.14. Figure 6 shows radiation from the sun passing through glass in a greenhouse onto the floor. The floor then emits radiation. State the name of the radiation emitted by the floor. (1 mark)  InfraredSECTION b (55 marks) Answer all the questions in this section 15. (a) On the axes provided, sketch a graph of Capacitance against the area of overlap of the plates of a parallel -plate capacitor.(1 mark) (b) (i) Draw a circuit diagram that may be used to investigate the discharging process of a capacitor. (2 marks) (ii) On the axes provided sketch the graph of potential difference between the plates against time for the discharging process. (1 mark) Determine the: (i) effective capacitance (3 marks) (ii) total charge stored (2 marks)Q = CV =2.22 x 10-6 x 6 = 1.332 x 10-5 C (iii) potential difference across the 4uF capacitor(2 marks) V=Q/C =1.33 x 10-5/ 4 x 10-6 =3.33V 16. (a) Define the following terms as used in waves (i) Amplitude (1 mark)   Amplitude is the maximum displacement of a particle from the mean position.(ii) Waves length (1 mark)   Wavelength is the distance between two successive points in a wave which are in phase. OR  Distance between two successive crests or troughs in a transverse wave/between two successive rarefaction or compressions in a longitudinal wave.(b) Figure 8 shows water waves approaching a straight reflector at a speed of 40cm’. (i) Draw on the diagram the reflected waves. (2 marks) (ii) Given that the distance between the source and the reflector is 15 cm determine: i). The wavelength of the waves (2 marks) Wavelength = distance/number of waves = 15/4 = 3.75cm (ii). The frequency of the waves (2 marks) =40 /3.75 — 10.67Hz (c) Figure 9 sows light rays from two coherent sources S1 and S2 falling on a screen. Dark and bright fringe s are observed between A and B. (i) State how:I. bright fringes are formed (1 mark)   Due to constructive interferenceII. dark fringes are formed (1 mark)   Due to destructive interference.(ii) State what is observed when light of a higher frequency is used. (1 mark)   The fringes get closer OR When the frequency is higher the wavelength

Questions and Answers 2019 Physics paper 1 Section A: (25 marks) 1. A micrometer screw gauge has a — 0.03 mm error. State the reading that is observed on the instrument s’hen used to measure the diameter of a wire whose actual diameter is 0.38 mm. (1 mark) Actual reading = 0.38mm (error) = 0.03 Meter reading = 0.35mm 2. Figure 1 shows a defective straw used to suck milk from a glass. It was observed that upon sucking the straw, milk did not rise up the straw. Explain this observation. (2 marks)   On sucking air rushes into the straw ✔ through the hole making it difficult✔to reduce pressure in the straw by sucking3. State two ways of reducing surface tension of a liquid. (2 marks)   Using detergents/impurities Raising the temperature4. Figure 2 shows a round bottomed flask containing a coloured liquid. The flask is fitted with a capillary tube. It is observed that on holding the flask with bare hands, the level of the liquid in the capillary tube initially drops slightly and then rises. Explain this observation. (3 marks) The flask absorbs heat from the hands and first expands ✔ hence level of liquid which expands more than the glass causing the rise. 5. figure, 3 shows two metal rods A and B of equal length made of the same material but different diameters. Wax is attached at one end of each rod . A source of heat is placed between the two metal rods State with a reason, what is observed on the wax. (2 marks)  Wax on rod B drops off first. The thicker rod conducts heat faster than the thinner one.6.On the axes provided, sketch a displacement — time graph for a trolley moving down a frictionless inclined plane till it reaches the end of the incline.(1 mark) 7. A student carrying a heavy box using the right fund is observed to lean towards the left hand side. Explain this observation. (2 marks)  The box shifts the position of the center of gravity of the system towards the right hand to maintain equilibrium. The student leans in the opposite direction8. Figure 4 shows a one meter long uniform rod of negligible weight supporting two weights. Determine the position of the fulcrum from O cm for the rod to remain in equilibrium. (3 marks)Taking moments about the fulcrum Sum of clockwise moments = sum of anticlockwise moments l5x = 10(75 — x (x — 5)10 = (80 — x)15 15x — 750 — l0x 25x = 1250 25x = 750 x = 50cm x = 30 hence fulcrum at 75 — 30 = 45 45 + 5 = 50 9. State the meaning of the term “radian” as a unit of measurement. ( 1 mark)   Radian is an angle subtended at the center of a circle by an arc of length equal to the radius of the circle.OR r = 360/2π 1 radian = 10. For a fluid flowing at a velocity V in a tube of cross-sectional area A, VA = assumptions made in deriving this equation. (2 marks) (i) Flowing steadily (ii) Incompressible (iii) Non-viscous 11. A stone of volume 800 cm3 experiences an upthrust of 6.5 N when fully immersed in a certain liquid. Determine the density of the liquid. (2 marks) ρ = m/v ρ = 650g/800cm3 12. Figure 5 shows two springs C and D of the same length and equal number of turns made from the same wire.   State with a reason which of the two springs can support a heavier load before attaining the elastic limit. (2 marks) C It has a smaller diameter hence a higher spring constant 13. Two boxes E and F of masses 2.0kg and 4.0kg respectively are dragged along a fictionists surface using identical forces. State with a reason which box moves with a higher velocity. (2 marks) E (20N)+ F — Ma, the smaller the mass, the higher the acceleration SECTION B (55 marks) Answer all the questions in this section 14. (a) A student is provided with five 20g masses, a meter rule, a spring with a pointer,a stand,a boss and a clamp. (i) In the space provided, sketch a labelled diagram of the setup that may be used in order to verify Hooke’s law using these apparatus. (3 marks) (ii) State two measurements that should be recorded in order to plot a suitable graph so as to verify Hooke’s law. (2 marks)  Force due to total mass hung. Extension produced by hanging masses(iii) Describe how the measurements made in (ii) can be used to determine the spring constant. (2 marks)   Plot a graph of force against extension. Determines the slope of the graph.(b) A helical spring stretches by 0.6 cm when Supporting a weight Of 40 g. Determine the extension when the same spring supports a weight of 65 g. (3 marks) k =f/e 0.40/0.60 =0.667 e=f/k 65/0.667 0.975cm 15.Figure 6 shows a bottle top opener being used to open a bottle.   15.(a) Indicate on the diagram the direction of the load and the effort. (2 marks) (b) State two ways in which an inclined plane can be made to reduce the applied effort when pulling a load along the plane. (2 marks)  Reducing the angle of inclination. Reducing the friction — using rollers, lubricants etc.(c) A block and tackle system has three pulleys in the upper fixed block and two pulleys in the lower movable block. (i) Draw a diagram to show how the system can be set up in order to lift a load and indicate the position of the load and effort. (3 marks) (ii) State the velocity ratio of the set up. (1 mark)(iii) In such a block and tackle system an effort of 200N is required to lift a load of 600 N. Determine its efficiency. (3 marks) 16. (a) State the meaning of the term “heat capacity.” (1 mark)   Heat capacity is the quantity of heat energy

Kenya Certificate of Secondary Education 2020 Physics paper 2 Section A (25 Marks) Answer all the questions in this section. 1. State the observation made on the image in a pin hole camera when the distance between the object and the pin hole is reduced.(2 marks) The image size increases/ becomes larger/ bigger/ magnified. 2. Figure 1 shows a gold leaf electroscope (a) Name the part labelled A.(1 mark) Protect the surrounding of the metal rod and leaf from damage or draughts /external effects external effects. The e.m.f. across it’s terminals (b) State the function of the part labelled B.(1 mark) 3. State two measurements that should be taken for one to decide whether a lead acid accumulator is due for charging. (2 marks) The emf across it’s terminals/Voltage/ pod across The relative density of the electrolyte/ density of acid/electrolyte (not liquid) 4. Explain what happens to the speed of a water wave as it moves from the shallow to the deep end in a ripple tank.(2 marks) the speed increases since the wavelength λ increases but the frequency is same because source is the same (no mark for contradiction) 5. The critical angle for a ray travelling from glass to air is 42°. Determine the refractive index of the glass.(3 marks) π = 1⁄sin c = 1⁄sin 42° = 1⁄0.669 = 1.495 (accept 2 dp – 1.49/ 1.50/ 1.494) 6. Figures 2(a) and 2(b) show two circuit diagrams with identical lamps and identical cells.State with a reason which of the bulbs will be brighter(2 marks) B.The two cells series provide a higher electromagnetic force/ potential difference/ current/ voltage 7. 7. Figure 3 shows an annular ring (uniformly distributed and must be on the surface) 8. When iron filings are sprinkled onto a bar magnet, it is observed that there are more iron filings at the ends than in the middle. Explain this observation.(2 marks) There is a greater magnetic force at the ends due to increased field lines at the ends of the bar magnet than at the centre of the bar magnet./ high flux density/ or due to higher concentration of field lines at the ends. 9. Draw a diagram to show a p-n junction connected in the reverse bias mode.(2 marks) (reject incomplete circuit) 10. A broadcasting station produces radio waves of wavelength 800 m. Determine their frequency (speed of air is 3 x 108ms-1)(2 marks) f = 3 x 108 λ 3 x 108/800 = 0.00375 x 108 Hz = 3.75 x 105Hz 11. Explain how x-rays are produced in the x-ray tube(2 marks) Electrons are produced by thermionic emission Electrons are accelerated by high voltage Electrons are suddenly stopped to produce x-rays/ stopped by hard surface (marks not tied. They are independent) 12. State the purpose of a fuse in an electrical circuit.(1 mark) To disconnect circuit when excess current flows( break)/ protect/ guard appliances from excess current/ electrical fire 13. Figure 4 shows circular water waves incident on a plane reflector placed at an angle to the path of the waves.Complete the diagram to show the reflected waves.(2 marks) curve correctly angle of reflection (check for correct shapes) (correct wavelength and angles) SECTION B (55 MARKS) 14.(a) State two ways of minimising power losses during the transmission of electric power.(1 mark) Stepping up the voltage/ current Use of good conductor cables/ thick cables (b) An electric cooker is rated 2.5 kW, 250 V. State the meaning of these values. (1 mark) The electric cooker has power output of 2500W when it operates at a potential of 250v, P = V1 (c) A consumer has the following appliances in the house: An electric iron rated 1500 W A water heater rated 500 W An electric cooker rated 2500 W Three bulbs each rated 60 W. The house is fitted with a 12 A fuse. Determine: (i) whether the consumer can connect all the appliances to the 240 V power supply at the same time;(4 marks) Total power = 1500 + 2500 + 500 +( 60×3) = 4680 W Total current required = 4680/240 = 19.5A (ii) the resistance of the heating element used in the electric cooker.(3 marks) Hence fuse blows and disconnects the current when it exceeds 10A ie, all appliances can’t be connected at the same time/ max current for all appliances connected is higher than the fuse rating. 15.(a) Describe how the focal length of a concave mirror can be determined using a screen and a metre rule.(1 mark) Using the mirror focus a distant object on to the screen Adjust the distance the screen & mirror to obtain a sharp image Measure the distance between the screen & the mirror – this is the focal length of the mirror (using the metre rule measure the distance between the screen and the mirror) (b) An object is placed 8cm from a concave mirror whose radius of curvature is 20cm. Determine the position of the image.(3marks) 1/f = 1/u + 1/v 1/v = 1/10 – 1/8 1/v = 4 – 5/10 v= 40cm (c) An object of height 10 cm is placed 30 cm from a converging lens of focal length 18 cm. (i) On the grid provided. draw a ray diagram to locate the position of the image formed.(3 marks) For diagram, check: Correct scale Correct rays Correct image post Correct tilt (ii) From the diagram in part (i), determine the: (I) image height;(2 marks) Image height = 15cm (II) image distance.(2 marks) Image distance = 45cm 16.(a) State two uses of radioactivity in medicine.(1 mark) Sterilization of medical equipment Treatment of malignant growths/ radio therapy/ killing cancerous cells / removing thyroid glands (b) The following is a nuclear reaction equation: 63Li + 10n → 31H + xyP Determine the values of x and y.(2 marks) x = 4 y= 2 (c) Figure 5 shows a radioactive element placed in an evacuated glass chamber. The element produces alpha, beta and gamma emissions. The three emissions pass through an electric field. (i)