# Physics Questions and Answers - Form 2 End of Term 3 Exams 2021

INSTRUCTIONS

• Answer ALL questions this section in the spaces provided.

SECTION A : (30 MARKS)

1. Figure 1 shows a micrometer with a negative error of 0.02mm used to measure the diameter
of a ball bearing.

Record the diameter of the ball. (2mks)
2. An oil drop of volume 0.4mm³ was placed on a clean water surface. It spread to form a monoatomic circular patch of area 2000mm². Use this data to calculate the diameter of a molecule of oil. (3mks)
3. A fixed mass of pure water was cooled from 20ºC to OºC. Sketch a graph of density of the water against temperature (2mks)
4. Two 10g masses are fixed onto two similar aluminium plates, one polished and the other painted black, using wax as shown in the figure below.

Give and explain the observation made. (2mks)
5. The figure below shows a charged leaf electroscope.

Given a dry glass rod and silk cloth, explain how you would determine the type of charge on the electroscope. (2mks)
6. State two advantages of alkaline accumulator over the lead-acid cell. (2mks)
7. The figure below shows two magnets whose North poles are brought close to each other.

Indicate the magnetic field pattern between the two magnets. (2mks)
8. The diagram shows a system in equilibrium with the uniform rule supported at Q and resting horizontally.

The rule is 1m long and weighs 1.8N. Calculate the weight of the block X. (3mks)
9. An object is placed infront of a concave mirror as shown in the figure below. Complete the diagram to show how the image is formed. (3mks)
10. State and explain what will happen to the freely suspended magnet when the switch S is closed. (2mks)
11. Three identical springs A, B and C are used to support a 15.5N weight as shown in the figure below.

If the weight of the horizontal beam is 0.5N, determine the extension of each spring given that 4N cause an extension of 1cm when using one spring. (3mks)
12. State one of the major differences between mechanical waves and electromagnetic waves. (2mks)
13. A boat sent an ultrasound signal to the bottom of the sea and its echo received after 10 seconds. If the wavelength of the ultrasound in water is 0.05m and the frequency of the transmitter is 50 KHz, calculate the depth of the sea. (3mks)

SECTION B: (40 MARKS)

1. Complete the diagram below to show how an image is formed in a pinhole camera. (3mks)
2. State two characteristics of the image above. (2mks)
4. If  = 30cm, y = 12cm and the heights of the image is 4cm, calculate the height of the object. (3mks)
1. The diagram below shows the wave profile of a transverse wave.
1. Determine
1. the amplitude of the wave. (1mk)
2. the wavelength of the wave in metres. (2mks)
3. the period of the wave if it takes 1.5 seconds to move from A to B. (3mks)
2. Calculate:
1. the frequency of the wave. (2mks)
2. the velocity of the wave. (2mks)
2. .
1. What is diffusion? (2mk)
2. A smoke cell contain a mixture of trapped air and smoke. The cell is brightly lit and viewed through a microscope. State and explain what is observed. (2mks)
3. A beaker is filled completely with water. A spoonful of common salt is added slowly. The salt dissolves and the water does not overflow.
1.  State why the salt is added slowly. (1mk)
2. Why doesn’t the water overflow? (1mk)
4. In the figure below, ammonia gas and acid gas diffuse and react to form a white deposit on the walls of a long glass tube as shown.
1. What conclusion can be made from this result of this experiment? (1mk)
2. How does the density of a gas affect the rate of diffusion? (1mk)
3. The experiment is performed at a lower temperature. State and explain what would happen to the rate of diffusion of the gases. (2mks)
1. Give four differences between mass and weight. (4mks)
2. Sate Pascal’s Principal. (1mk)
3. Name two applications of Pascal’s Principle. (2mks)
4. Figure 3 shows a U-tube containing two liquids L1 and L2 of densities 1.6g/cm³ and 0.8g/cm³ respectively in equilibrium.

Given that h2 = 18cm, determine the value of h1. (3mks)

## MARKING SCHEME

1.  + 5.5
0.38
5.88 1 (5.88)
+ 0.02
5.90mm 1 (5.90)
= 9.112m

2000d     = 0.4
d             = 0.4
2000
=2 x 10-4mm
=2 x 10-7m
3. .
4.
• Mass on dull tin plates falls off before mass on polished tin.
• Dull tin absorbs heat faster than polished tin (it heats up faster and wax on it melts before
• Charge the glass rod by rubbing it with silk.
• Place the rod near the cap of the electroscope.
• If the divergence of the leaf increases, the electroscope is positive.
• If the divergence of the leaf decreases, the electroscope is negative.
5.
• It can give a bigger current.
• It can be left in the discharge condition for a long time without damage. 1, 1 any 2 correct
• It requires less attention.
• It is lighter.

6.
• Magnet will be repelled 1
• Coil is magnetized with end near magnet acquiring North Pole 1
7. For A and B
4N – 1cm
8N -  x 8
4
= 2cm each 1
For C 4N – 1cm
15.5N  -1 x 15.5
4N
= 3.875cm 1
8.
• Mechanical waves require a material medium. 1
• Electromagnetic waves do not require a material medium. 1

1. Velocity of sound  = 50,000 x 0.05
= 2500m/s
Depth = 2500 x 10
2
= 12,500m

1. Level of fluid in C is higher than level in B.
2. In B the fluid flow with relatively high velocity hence low pressure. While in be the velocity is low hence high pressure.

SECTION B

1.  (Check that rays get to screen)
• Real 1mk
• Inverted 1mk
2. Becomes
• Brighter
• Blurred
• Bigger
Any two (2mks)
1.
1. 2cm
2. 4cm = 0.04m
3. 3 oscli → 1.55
1 0scli → ?
Period =  1.55
3
= 0.53
1.
1.  f= 1
T
1
0.5
= 2Hz
2. V = λf
= 2 x 0.04
= 0.08m/s
2.
1. It is the spreading of particles from regions of high concentration to those of low concentration.
2.
• Bright specks are seen in continuous random motion. 1mk
• This is because of uneven bombardment by the invisible particles or molecules of air.
3.
1. To avoid splashing the water.
2. Because the salt particles fitted well in the spaces between the water molecules.
1. Ammonia gas diffuses at faster rate than hydrochloric acid gas.
2. A denser gas diffuses at a slower rate than the lighter one.
• Diffusion takes longer time
• because the particles are at low kinetic energy moves slowly. 1mk
3.

1.  Mass Weight Quantity of matter in a body.Measured in kilogram.Same everywhere. Measured using a beam balance.Has magnitude only. Pull of gravity on a body.Measured in Newton’s.Changes from place to place.Measured using a spring balance.Has both magnitude and direction Any four correct
2. Pressure applied at one part of a liquid is transmitted equally to all other parts of the enclosed liquid.
3.
1. Hydraulic lift
2. Hydraulic brake system

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