Free KCSE Physics Topical Questions KNEC Standards

K.C.S.E Physics Q & A - MODEL 2019PP1QN18

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN18

(a) Figure 9 shows a graph of pressure against temperature for a fixed mass of gas at constant volume.

From the graph, determine the values of n arid e given that P = nT + c where n and c are constants.
(b) Explain why it is not possible to obtain zero pressure of a gas in real life situation.
(c) A fixed mass of a gas occupies 1.5 X 10^-3 m^-3 at a pressure of 760 mmHg and a temperature of 273 K. Determine the volume the gas will occupy at a temperature of 290K and a pressure of 720 mmHg.
(d) State any three assumptions made in kinetic theory of gases.

answers

(b) It is not possible to reduce the pressure of a gas to zero since by then most of the temperatures are very low hence the gas liquefies.

(d) Assumptions of the kinetic theory of gases:
Attraction of between the molecules is negligible.
Volume of the molecule is negligible compared to the volume of the container occupied by the gas.
The molecules undergo elastic collisions.
The length of time of a collision is negligible compared to the time between collisions.

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K.C.S.E Physics Q & A - MODEL 2019PP1QN17

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN17

(a) State what ¡s meant by Brownian Motion.
(b) Figure 8 shows the graph of velocity against time For a small steel ball Falling in a viscous liquid.

(a) State what ¡s meant by Brownian Motion. (1 mark) (b) Figure 8 shows the graph of velocity against time For a small steel ball Falling in a viscous liquid. (i) Describe the motion of the steel ball as represented by part OA (ii) Explain why the velocity of A and B is constant (c)A student throws a tennis ball vertically upwards from the ground and it lands back after 8 seconds.( acceleration due to gravity g =10ms-2) Determine the: (i) maximum height reached by the ball iii) velocity with which the ball hits the ground. (3 marks)

(i) Describe the motion of the steel ball as represented by part OA
(ii) Explain why the velocity of A and B is constant
(c)A student throws a tennis ball vertically upwards from the ground and it lands back after 8 seconds.( acceleration due to gravity g =10m/s2)
Determine the:
(i) maximum height reached by the ball
iii) velocity with which the ball hits the ground.

answers

(a) Continuous random motion of particles.
(b) (i) It accelerates, velocity increases.
(ii) As the ball falls through the fluid, the Viscous drag increases until the sum of the Viscous drag and the upthrust becomes equal the weight of the steel ball, hence the resultant force becomes zero.

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K.C.S.E Physics Q & A - MODEL 2019PP1QN16

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN16

(a) State the meaning of the term “heat capacity.”
(b) State how pressure affects the melting point of a substance.
(c)Figure 7 shows a set tip of apparatus that may be used to apparatus the specific latent heat of vaporization of steam

(I) Describe how the mass of condensed steam is determined.
(ii) Other than mass and time, state two other measurements that should be taken during the experiment.
(iii) Show how the measurements in (c)(ii) can be used to determine the specific latent heat of vaporization of water.
(iv) State the precaution that should be taken so that the mass of the condensed steam measured corresponds to the actual mass of steam collected during the time recorded in the experiment
(v) State why it is not necessary to measure temperature in in the set up

answers

(a) Heat capacity is the quantity of heat energy required to raise the temperature of a substance by 1K.
(b) - Increase in pressure lowers the melting point while decrease in (1 mark) pressure raises/increases the melting point.
(c) (i) - Measure the mass of the empty beaker M1.
Measure the mass of the beaker plus the condensed steam M2
Get the difference between the two masses (M2 —M1) = M
(ii) - Voltage
Current

(iv) - Start timing when the steam drops start forming out steadily and Stop immediately the beaker is withdrawn.
(V) Steam is produced at boiling point where temperature is constant.

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K.C.S.E Physics Q & A - MODEL 2019PP1QN15

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN15

(a)Figure 6 shows n bottle top opener being used to open a bottle.

Indicate on the diagram the direction of the load and the effort.
(b) State two ways ¡n which an inclined plane can be made to reduce the applied effort when pulling a Load along the plane.
(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 arid indicate the position of the load and effort.
(ii) State the velocity ratio of the set up.
(iii) In such a block and tackle system an effort of 200N is required to lift a load of 600N. Determine its efficiency

answers

(b)Reducing the angle of inclination.
Reducing the friction — using rollers, lubricants etc.

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K.C.S.E Physics Q & A - MODEL 2019PP1QN14

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN14

(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 set up that may be used in order to verify Hooke’s law using these apparatus.
(ii) State two measurements that should be recorded in order to plot a suitable graph so as to verify Hooke’s law.
(iii) Describe how the measurements made in (ii) can be used to determine the spring constant.

(b) A helical spring stretches by 0.6cm when Supporting a weight of 40 g. Determine the extension when the same spring Supports a weight of 65 g.

answers

(ii) Force due to total mass hung.
Extension produced by hanging masses.
(iii) — Plot a graph of force against extension.
Determines the slope of the graph

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K.C.S.E Physics Q & A - MODEL 2019PP1QN13

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN13

Two boxes E and F of masses 2.0 kg and 4.0 kg respectively arc dragged along a frictionless surface using identical forces. State with a reason which box moves with a higher velocity.

answer

E (20N)
F = Ma, the smaller the mass, the higher the acceleration

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K.C.S.E Physics Q & A - MODEL 2019PP1QN12

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN12

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.

answer

C
It has a smaller diameter hence a higher spring constant.

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K.C.S.E Physics Q & A - MODEL 2019PP1QN11

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN11

A stone of volume 800 cm³ experiences an upthrust of 6.5N when fully immersed in a certain liquid. Determine the density of the liquid.

answer

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K.C.S.E Physics Q & A - MODEL 2019PP1QN10

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN10

For a fluid flowing at a velocity V in a tube of cross-sectional area A, VA =constant. State two assumptions made in deriving this equation.

answer

The assumptions are: the fluid is

(i) flowing steadily,
(ii) incompressible,
(iii) non-Viscous.

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State the meaning of the term “radian” as a Unit of measurement.

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN09

State the meaning of the term “radian” as a Unit of measurement.

answer

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K.C.S.E Physics Q & A - MODEL 2019PP1QN08

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN08

Figure 4 shows a one meter long uniform rod of negligible weight supporting two weights.

Determine the position of the fulcrum from 0 cm for the rod to remain in equilibrium.

answer

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A student carrying a heavy box using the right hand is observed to lean towards the left hand side. Explain this observation.

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN07

A student carrying a heavy box using the right hand is observed to lean towards the left hand side. Explain this observation.

answer

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 direction.

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K.C.S.E Physics Q & A - MODEL 2019PP1QN06

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN06

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.

answer

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K.C.S.E Physics Q & A - MODEL 2019PP1QN05

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN05

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.

answer

Wax on rod B drops off first.
The thicker rod conducts heat faster than the thinner one.

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K.C.S.E Physics Q & A - MODEL 2019PP1QN04

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN04

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.

answer

The flask absorbs heat from the hands and first expands hence level of liquid which expands more than the glass causing the rise.

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State two ways of reducing the surface tension of a liquid.

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN03

State two ways of reducing the surface tension of a liquid.

answer

Using detergents/impurities
Raising the temperature

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K.C.S.E Physics Q & A - MODEL 2019PP1QN02

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN02

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.

answer

On sucking air rushes into the straw through the hole making it difficult to reduce pressure in the straw by sucking.

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K.C.S.E Physics Q & A - MODEL 2019PP1QN01

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN01

A micrometer screw gauge has a -0.03 mm error. State the reading that is observed on the instrument when used to measure the diameter of a wire whose actual diameter is 0.38 mm.

answer

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K.C.S.E Physics Q & A - MODEL 2019PP2QN18

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP2QN18

(ii) Describe how a magnet can be demagnetised using the electrical method.
(b) You are provided with two iron bars P and Q. One of the bars is magnetized while the other is not. Explain how themagnetized bar can be identified without using a magnet or magnetic material.
(c)Figure 12 shows two identical copper coils X and Y placed close to each other. Coil X is connected to a DC power supply while coil Y is connected to a galvanometer.

Explain what is observed on the galvanometer When the Switch is closed.
(ii) State What is observed on the galvanometer when the switch is opened.
(iii) State what wou1d be observed if the number of turns in coil Y is doubled.

answers

(a) Place the bar magnet inside a solenoid placed in the an East-West direction then pass an alternating current through the solenoid
(b) Suspend each of the bars through its center of gravity and set it swinging in a horizontal plane shows a vertical axis through its centre
The magnetized bar will always come to rest in a north-south direction
(c) (i) The galvanometer pointer first deflects then moves back when the switch is closed a current builds up in a coil X and due to change influx linkage an emf is induced in coil Y making an induced current to flow through the galvanometer during the time current in coil X is rising. When current through coil X is steady no induced current flows through the galvanometer since there is no change in flux linkage
Therefore pointer deflects back
(ii) Pointer deflects in the opposite direction.
(iii) Magnitude of deflection increases

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K.C.S.E Physics Q & A - MODEL 2019PP2QN17

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP2QN17

(a) Figure 10 shows a ray of light travelling from glass to air.

Determine the:
(i) critical angle of the glass — air interface
(ii) refractive index of glass
(b) Apiece of metal is embedded at the centre of an ice block 15cm from the surface of the ice. Given that the refractive index of ice is 1.32, determine how far from the surface of the ice block the metal appears to be.
(c) Figure 11 shows, two rays of incident on a diverging lens.

Complete the ray diagram to show the path of the rays after passing through the lens.
(d) (i) State two differences between the human eye and a camera lens.
(ii) State the name of the part of the eye that enable the lens to focus images of objects at different distances.

ANSWERS

(d)(i) Eye has a variable focal length whole the focal length of camera lens is fixed
Image distance from the lens is almost constant in the eye while in a camera it can be varied
Eye lens is muscle while glass/clear plastic
(ii) Ciliary muscles

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K.C.S.E Physics Q & A - MODEL 2019PP2QN16

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP2QN16

(a) Define the following terms as used in waves:
(I) Amplitude
(ii) Wavelength
(b) Figure 8 shows water waves approaching a straight reflector at a speed of 40 cm/s.

(I) Draw on the diagram the reflected waves.
(ii) Given that the distance between the source and the reflector is 15 cm determine:
I. the wavelength of the waves
II. the frequency of the waves
(c) Figure 9 Shows light rays from two coherent sources S1 and S2 falling on a screen.
Dark and bright fringes are observed between A and B

(i) State how:
I. bright fringes are formed
II. dark fringes are formed
(ii) State what is observed when light of a higher frequency is used.

ANSWERS

(a)(i)Amplitude is the maximum displacement of a particle from the mean position
(ii)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 rarefaction or compressions in a longitudinal wave.

(c)(I) due to constructive interference
(II) due to destructive interference
(ii) The fringes get closer
OR
When the frequency is higher the wavelength reduces hence the fringe separation decreases

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K.C.S.E Physics Q & A - MODEL 2019PP2QN15

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP2QN15

(a) On the axes provided, sketch a graph of capacitance against the area of overlap of the plates of a parallel-plate capacitor.

(b) (I) Draw a circuit diagram that may be used to investigate the discharging process of a capacitor.
(ii) On the axes provided sketch the graph of potential difference between the plates against time for

the discharging process.
(c) Figure 7 shows three capacitors connected to a 6V battery.