Free KCSE Physics Topical Questions KNEC Standards

The figure below shows the path of a ray of light passing through a rectangular glass block placed in air

23/10/2021

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The figure below shows the path of a ray of light passing through a rectangular glass block placed in air

Calculate the refractive index of glass (2mks)

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The figure below shows an object placed in front of a concave mirror. By use of correct ray diagram, locate the position of image

23/10/2021

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The figure below shows an object placed in front of a concave mirror. By use of correct ray diagram, locate the position of image

Solution

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The figure bellows shows a wave profile for a wave whose frequency is 2HZ

23/10/2021

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The figure bellows shows a wave profile for a wave whose frequency is 2HZ

Determine the value of t₃(s) (2mks)

Solution

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A 240v mains transformer has 800 turns in the primary and N turns in the secondary. It is used to supply energy to a 12v/21w lamp

21/10/2021

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(a) A 240v mains transformer has 800 turns in the primary and N turns in the secondary. It is used to supply energy to a 12v/21w lamp.

(i) Calculate the number of turns in the secondary (2mks)

(ii) What is the efficiency of the transformer if the current drawn from the 240V mains is 100mA (2mks)

The circuit above shows a step-down transformer used to light a lamp of resistance.

Calculate.

(i) the reading of voltmeter, V, with, S, open (2mks)

(ii) the reading of the ammeter A with S closed (neglect the effective resistance of the secondary winding) (2mks)

(iii) the power dissipated in the lamp (2mks)

(iv) the primary current if the transformer is 90% efficient (3mks)

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Explain why bulbs in along corridor are not wired in series

21/10/2021

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(a) Explain why bulbs in along corridor are not wired in series (2mks)

High resistance, dim light
When one goes off, all others go off

(b) An electric cooker has an oven rated 2500w, a grill rated 1500w and two plates each of 1000W. This cooker operates directly from 240v supply. What is the costs of operating all the parts at once for 30 minutes if electricity costs sh.10.00 per unit? (3mks)

(c) Study the figure below

(i) What name is given to the fitting in the diagram (1mk)

3 pin plug

(ii) Identify the parts labeled (2mks)

A

Neutral wire

B

Earth wire

C

Live wire

D

Fuse

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Give two advantages of a circuit breaker instead of a fuse in domestic wiring

21/10/2021

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Give two advantages of a circuit breaker instead of a fuse in domestic wiring (2mks)

It disconnects current immediately unlike the fuse that takes time to melt
It is not damaged

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Give a reason why gases are poor transmitters of sound

20/10/2021

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Give a reason why gases are poor transmitters of sound (1mk)

Molecules in gases are much further apart

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A student set-up the apparatus as shown below to determine the power of an electric heater.

19/10/2021

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A student set-up the apparatus as shown below to determine the power of an electric heater

A student set-up the apparatus as shown above to determine the power of an electric heater

(a)
(i) Other than time, state the measurements that would be used to determine the quantity of heat P absorbed by ice in a unit time (2mks)

Current, voltage (p.d) mass of water collected temperature of the melt

(ii) Complete the circuit to show the connection of the essential circuit components (2mks)

(iii) Describe how the student would proceed to determine P (3mks)

Switch on the current and start the clock simultaneously
Record the steady venus current I and P.d.v
Note the temperature of the melt( should be 0oC)
Weighs the melt to obtain its mass m, collected over a known length of time , t

Apply Ivt=mlf

(iv) Give a reason why P may not be equal to the value indicated by the manufacturer (1mk)

It may not be operating at its optimum conditions of p.d and temperature, T. the heater also absorbs heat

(b) In another experiment, 100g of hot water at 90^oC was mixed with 20g of ice at 0^oC in a lagged plastics colorimeter. After stirring, all the ice melted and the temperature of the mixture was found to be 61.5^oC. Determine the latent heat of fusion of ice (3mks)

(Specific heat capacity of water = 4200Jkg^-1k^-1)

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The diagram below shows two trolleys, A and B connected to each other by an elastic strip of negligible mass. The trolleys are pulled apart on a smooth plane till tension in the elastic strip is 4.0N and are then released suddenly

18/10/2021

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The diagram below shows two trolleys, A and B connected to each other by an elastic strip of negligible mass. The trolleys are pulled apart on a smooth plane till tension in the elastic strip is 4.0N and are then released suddenly

(a) State with reason the total momentum of the trolleys when they are just released (2mks)

Zero (0) –It is because their velocities are still zero/ They are still stationary

(b) Calculate the initial acceleration of trolley A when released (3mks)

(c) The velocity of the trolley B is 0.9ms^-1 just before it collides with A. Determine the velocity of A just before the collision

(d) Which trolley covers a longer distance before collision? Explain (2mks)

trolley A, because of it moves with high velocity

(e) Explain why the elastic strip may not stretch to the same original length after impact (2mks)

Friction force

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Complete the figure below to show how a single pulley can be arranged to a velocity ratio(V.R) of 2

16/10/2021

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Complete the figure below to show how a single pulley can be arranged to a velocity ratio(V.R) of 2 (2mks)

Complete the figure below to show how a single pulley can be arranged to a velocity ratio(V.R) of 2

Solved ...

a single pulley arranged to a velocity ratio(V.R) of 2

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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 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 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 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

2 Comments

K.C.S.E Physics Q & A - MODEL 2019PP2QN14

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP2QN14

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.

answer

Infrared

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State how the intensity of X-rays in an X-ray tube can be increased.

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP2QN10

State how the intensity of X-rays in an X-ray tube can be increased.

answer

By increasing the heating current in order to produce more electrons

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State two uses of gamma rays in medicine.

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP2QN08

State two uses of gamma rays in medicine.

answers

To sterilize medical equipment
To kill cancerous cells and malignant growths in the body

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K.C.S.E Physics Q & A - MODEL 2019PP2QN07

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP2QN07

Figure 3 shows a cell connected in series with an ammeter, a 2 ohms resistor and a switch.A voltmeter 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 ohms , determine the ammeter reading when the switch is closed.

answer

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State the reason why the current produced by a simple cell falls rapidly when the cell is being used,

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP2QN06

State the reason why the current produced by a simple cell falls rapidly when the cell is being used,

answer

Polarization

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K.C.S.E Physics Q & A - MODEL 2018PP2QN19

29/7/2020

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K.C.S.E Physics Q & A - MODEL 2018PP2QN19

Figure 8 shows two waves of nearly equal frequency produced simultaneously.

On the space provided, sketch the resultant of the two waves (beats).
(b) Figure 9(a) and 9(b) show barriers placed in the path of plane waves.

On each figure, sketch the pattern of waves after they pass the barrier.
(c) Figure 10 shows a displacement—distance graph for a certain wave motion.

(i) Indicate on the figure with letters A and B any two points that are in phase.
(ii) Determine the:
(I) amplitude of the wave
(II) wavelength of the wave
(iii) Given that the frequency of the waves is 50 Hz, determine the:
(I) period
(II) speed of the wave

answers

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K.C.S.E Physics Q & A - MODEL 2018PP2QN17

29/7/2020

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K.C.S.E Physics Q & A - MODEL 2018PP2QN17

(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
(ii) Wavelength
(iii) Velocity

(b) (i) A biconvex lens forms an upright image twice the size of the object. If the focal length of the lens is 20cm, determine the object distance.
(ii) State two optical instruments which produce a magnified real image using a Convex lens.
(c) State one difference between the working of the human eye and the lens of a camera.
(d) A lens of focal length 2Ocm forms a virtual image when an object is placed 60cm from the lens. State with a reason the type of lens used.

answers

(a)(i) No change in frequency
(ii) Wavelength increases
(iii) Velocity increases

(ii) a film projector
A compound microscope
(c) In a camera focusing is done by changing the distance between the lens and the film. While in the eye focusing is done by changing the curvature of the lens.
d) Diverging lens
Forms a virtual image when the object distance is greater than the focal length.

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K.C.S.E Physics Q & A - MODEL 2018PP2QN16

29/7/2020

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K.C.S.E Physics Q & A - MODEL 2018PP2QN16

(a) State the meaning of the following terms:
(i) Photoelectric effect
(ii) Threshold frequency
(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 microammete

(î) Explain how the microammeter reading is affected when the intensity of the incident light is increased.
(ii) State the reason why the tube is evacuated
(c) Figure 6 shows a graph of maximum kinetic energy (KE max) of photoelectrons against the frequency of the incident radiation.

From the graph, determine:
(i) Plank’s constant h,
(ii)the threshold wavelength given that the speed of light C is 3.0 x 10⁸ms^-1

answers

(a)(i) The emission of electrons from a metal surface when light/electromagnetic radiations shine on it.
(ii) The minimum frequency of radiation required to eject electrons from a metal surface.
(b)(i) Increased intensity increases the number of electrons emitted hence a higher current reading on the microammeter.
(ii) To minimize collisions between electrons and air molecules which would cause loss of energy.

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K.C.S.E Physics Q & A - MODEL 2018PP2QN14

29/7/2020

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K.C.S.E Physics Q & A - MODEL 2018PP2QN14

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.

answer

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<<Previous

​The figure below shows the path of a ray of light passing through a rectangular glass block placed in air

​Calculate the refractive index of glass (2mks)

​The figure below shows an object placed in front of a concave mirror. By use of correct ray diagram, locate the position of image

Solution

The figure bellows shows a wave profile for a wave whose frequency is 2HZ

Determine the value of t3(s) (2mks)

Solution

(a) A 240v mains transformer has 800 turns in the primary and N turns in the secondary. It is used to supply energy to a 12v/21w lamp. ​

(i) Calculate the number of turns in the secondary (2mks)

(ii) What is the efficiency of the transformer if the current drawn from the 240V mains is 100mA (2mks)

​Calculate.

(i) the reading of voltmeter, V, with, S, open (2mks)

(ii) the reading of the ammeter A with S closed (neglect the effective resistance of the secondary winding) (2mks)

(iii) the power dissipated in the lamp (2mks)

(iv) the primary current if the transformer is 90% efficient (3mks)

​(a) Explain why bulbs in along corridor are not wired in series (2mks)

​(b) An electric cooker has an oven rated 2500w, a grill rated 1500w and two plates each of 1000W. This cooker operates directly from 240v supply. What is the costs of operating all the parts at once for 30 minutes if electricity costs sh.10.00 per unit? (3mks)

​(c) Study the figure below

​(i) What name is given to the fitting in the diagram (1mk)

​(ii) Identify the parts labeled (2mks)

A

B

C

D

Give two advantages of a circuit breaker instead of a fuse in domestic wiring (2mks)

​Give a reason why gases are poor transmitters of sound (1mk)

(a) ​(i) Other than time, state the measurements that would be used to determine the quantity of heat P absorbed by ice in a unit time (2mks)

​(ii) Complete the circuit to show the connection of the essential circuit components (2mks)

​(iii) Describe how the student would proceed to determine P (3mks)

​(iv) Give a reason why P may not be equal to the value indicated by the manufacturer (1mk)

(b) In another experiment, 100g of hot water at 90oC was mixed with 20g of ice at 0oC in a lagged plastics colorimeter. After stirring, all the ice melted and the temperature of the mixture was found to be 61.5oC. Determine the latent heat of fusion of ice (3mks)

​(a) State with reason the total momentum of the trolleys when they are just released (2mks)

​(b) Calculate the initial acceleration of trolley A when released (3mks)

(c) The velocity of the trolley B is 0.9ms-1 just before it collides with A. Determine the velocity of A just before the collision

​(d) Which trolley covers a longer distance before collision? Explain (2mks)

​(e) Explain why the elastic strip may not stretch to the same original length after impact (2mks)

Complete the figure below to show how a single pulley can be arranged to a velocity ratio(V.R) of 2 (2mks)

Solved ...

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

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

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

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

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

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

K.C.S.E Physics Q & A - MODEL 2019PP2QN14

State how the intensity of X-rays in an X-ray tube can be increased.

State two uses of gamma rays in medicine.

K.C.S.E Physics Q & A - MODEL 2019PP2QN07

State the reason why the current produced by a simple cell falls rapidly when the cell is being used,

K.C.S.E Physics Q & A - MODEL 2018PP2QN19

K.C.S.E Physics Q & A - MODEL 2018PP2QN17

K.C.S.E Physics Q & A - MODEL 2018PP2QN16

From the graph, determine: (i) Plank’s constant h, (ii)the threshold wavelength given that the speed of light C is 3.0 x 108ms-1

K.C.S.E Physics Q & A - MODEL 2018PP2QN14

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FREE NOVELS

The figure below shows the path of a ray of light passing through a rectangular glass block placed in air

Calculate the refractive index of glass (2mks)

The figure below shows an object placed in front of a concave mirror. By use of correct ray diagram, locate the position of image

Determine the value of t₃(s) (2mks)

(a) A 240v mains transformer has 800 turns in the primary and N turns in the secondary. It is used to supply energy to a 12v/21w lamp.

Calculate.

(a) Explain why bulbs in along corridor are not wired in series (2mks)

(b) An electric cooker has an oven rated 2500w, a grill rated 1500w and two plates each of 1000W. This cooker operates directly from 240v supply. What is the costs of operating all the parts at once for 30 minutes if electricity costs sh.10.00 per unit? (3mks)

(c) Study the figure below

(i) What name is given to the fitting in the diagram (1mk)

(ii) Identify the parts labeled (2mks)

Give a reason why gases are poor transmitters of sound (1mk)

(a)
(i) Other than time, state the measurements that would be used to determine the quantity of heat P absorbed by ice in a unit time (2mks)

(ii) Complete the circuit to show the connection of the essential circuit components (2mks)

(iii) Describe how the student would proceed to determine P (3mks)

(iv) Give a reason why P may not be equal to the value indicated by the manufacturer (1mk)

(b) In another experiment, 100g of hot water at 90^oC was mixed with 20g of ice at 0^oC in a lagged plastics colorimeter. After stirring, all the ice melted and the temperature of the mixture was found to be 61.5^oC. Determine the latent heat of fusion of ice (3mks)

(a) State with reason the total momentum of the trolleys when they are just released (2mks)

(b) Calculate the initial acceleration of trolley A when released (3mks)

(c) The velocity of the trolley B is 0.9ms^-1 just before it collides with A. Determine the velocity of A just before the collision

(d) Which trolley covers a longer distance before collision? Explain (2mks)

(e) Explain why the elastic strip may not stretch to the same original length after impact (2mks)

From the graph, determine:
(i) Plank’s constant h,
(ii)the threshold wavelength given that the speed of light C is 3.0 x 10⁸ms^-1