Physics Paper 2 Questions and Answers - Moi Tea Mock Examinations 2022

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Questions

State the property of light suggested by the formation of shadows. (1 mark)
The figure below shows a sharp pin fixed on a cap of leaf electroscope. The electroscope is highly charged and then left for sometime.

Explain why the leaf collapses. (2 marks)
1. The figure below shows an object O placed infront of a plane mirror.
2. On the same diagram, draw rays to locate the position of the image I as seen from the eye E. (2 marks)
1. State the basic law of magnetism. (1 mark)
2. The figure below shows how magnets are stored in pairs with keepers at the ends.
  
  Explain how this method of storing helps in retaining magnetism longer. (2 marks)
Why is a convex mirror better than plane mirror when used as a driving mirror? (1 mark)
The figure 2 shows a circuit diagram with cells in parallel. Each cell has e.m.f of 1.5V and internal resistance of 0.5Ω and the resistance of the bulb is 6Ω each. Determine the ammeter reading when the switch is closed. (3mks)
An appliance is rate 2.5KW, 240V a.c 50Hz. Explain the meaning of the rating(figures) on this appliance. (2mks)
The following are electromagnetic waves. Arrange them according to their increasing frequency. Gamma rays, microwaves, ultra-violet, TV waves and blue light. (1mk)
Distinguish between a transformer and induction coil. (2mks)
1. Distinguish between a transverse and a longitudinal wave. (1 mark)
2. Determine the frequency of the wave shown below. (2 marks)
State one reason why ultrasound is preferred to audible sound in echo-sounding. (1 mark)
An electric heater rated 240V, 3000W is to be connected to a 240V mains supply, through a 10A fuse. Determine whether the fuse is suitable or not. (3 marks)
Kiai noticed that any time he a light from his car and close the door holding the metallic hand he get a slight shock. Explain. (2mks)

SECTION B (55 MARKS)
Answer all the questions from this section in the spaces provided.

1. A transformer with 2000 turns in the primary circuit and 150 turns in the secondary circuit has its primary circuit connected to a 800Va.c. source. It is found that when a heater is connected to the secondary circuit it produces heat at the rate of 1000W. Assuming 100% efficiency, determine the:
  1. Voltage in the secondary circuit. (2 marks)
  2. Current in the secondary circuit. (1 mark)
  3. State the type of transformer represented above. (1 mark)
2. 1. State the reason why long distance power transmission is done at a very high voltage and using thick cables. (1 mark)
  2. Calculate the cost of using the following appliances in one month (30 days) of the company rate is Ksh.9.50 per unit.
    1. A 2000W water heater for 2 hours per day.
    2. A 75W bulb for 10 hours per day.
    3. An 1500W electric iron for 1 hour per day. (3 marks)
  3. Find the total monthly bill for the above household if in addition to the energy consumed, the power company charges each consumer.
    1. A standing charge of Ksh.200.
    2. Fuel cost levy at 70 cents per unit. (2 marks)
1. State two ways in which one can increase the strength of an electromagnet. (2 marks)
2. The following figure shows a conductor placed in a magnetic field. Indicate on the diagram the direction of motion of part AB of the conductor. (2mks)
3. A cell drives a current of 5A through a 1.6Ω resistor. When connected to a 2.8Ω resistor, the current that flows in 3.2A. Find E and r for the cell. (4 marks)
4. Calculate the length of a nichrome resistance wire of cross-sectional area 7 ×10^ˉ8m² required to make a resistor of 10 ohms. (Take resistivity of nichrome = 1.10 × 10^ˉ6Ωm). (3 marks)
5. 1. In figure below, calculate the p.d across resistor R. (2 marks)
  2. Current in the primary circuit. (2 marks)
The figure below shows rays of light entering a human eye which has a defect.
1. 1. Name the defect. (1mk)
  2. State 2 possible causes of the defect. (1mk)
2. Define the accommodation. (1mk)
3. A small bright object O lies at the bottom of a beaker containing water of depth h cm. A convex lens of focal length 15cm is held at the surface of water. The lens forms an image of O at 45cm from the surface of water.
  Taking the refractive index of water to be ⁴/₃, determine:
  1. the apparent depth of the object(2mks)
  2. the real depth h, of the object (2mks)
4. A ray of light is incident at right angles to the face AB, of a right angled isosceles prism of Refractive index 1.6 as shown in the figure below.
  
  If the prism is surrounded by a liquid of refractive index 1.40, determine:
  1. The angle of incidence on the face BC. (2mk)
  2. The angle of refraction on the face BC. (3mks)
1. State two ways through which the rate of evaporation of a liquid may be increased. (2 marks)
2. A metal of mass 10kg is heated to 120ºC and then dropped into 2kg of water. The final temperature of the mixture is found to be 50ºC. Calculate the initial temperature of the water. (Specific heat capacity of the metal and water is 450JKgˉ¹Kˉ¹ and 4200JKgˉ¹Kˉ¹ respectively). (3mks)
3. Give the property of water which makes it suitable for use as a coolant in machines. (1 mark)
4. Formation of ice on roads during winter in cold countries is known to hamper vehicles.
  State two ways in which the melting point of ice may be lowered to solve this problem. (2 marks)
5. Some ether is put in a combustion tube and two glass tubes inserted into the tube through a cork as shown in the figure below. The combustion tube is then put into a small beaker containing some water and a thermometer dipped in the water. When air is blown into the ether as shown, the reading in the thermometer lowers. Explain this observation. (2 marks)
1. An object is released to fall vertically from height of 100m. At the same time another object is projected vertically upward with velocity of 40m/s.
  1. Calculate the time taken before the objects meet (3mks)
  2. At what height do the objects meet? (2mks)
2. A string of negligible mass has a bucket tied at the end. The string is 60cm long and the bucket has a mass of 45g. The bucket is swung horizontally making 6 revolutions per second. Calculate
  1. The angular velocity (2mk)
  2. The angular acceleration (2mks)
  3. The tension on the string (2mks)
  4. The linear velocity (1mk)

Marking Scheme

Rectilinear propagation. ✓¹
The negatively charged electrons will move away from the gold leaf towards the + charges on the sharp pin and the leaf will collapse.
1. Unlike poles attract, like poles repel ✓¹
2. The keepers become magnetized thus neutralizing ✓ the pole; this reduces repulsion at the poles ✓ thus helping in retention of magnetism.
It has a wider field of view than that of a plane mirror. ✓
- Total resistance R= 6+6+0.5Ω=12.5Ω
  Current I= ^V/_R=^3.0/_12.5=0.24A
  Total resistance R= 6+6+0.5Ω=12.5Ω
  Current I= ^V/_R=^3.0/_12.5=0.24A
  Total resistance R= 6+6+0.5Ω=12.5Ω
  Current I= ^V/_R=^3.0/_12.5=0.24A
When the terminals of the heater are at a p.d of 240V and connected to an alternating current of frequency 50Hz, it converts 2500J of electrical energy to 2500 J of heat energy per second.
TV waves----microwaves—blue light---Ultra-violet—gamma rays.
- Transformer uses a.c only while induction coil uses d.c
- Transformer produces a humming sound while induction coil is quiet

Transverse	Longitudinal wave
Displacement of particles in the wave is perpendicular to the direction of wave motion.	Displacement of particles in the wave is parallel to the direction of wave motion.
Requires no medium for propagation.	Requires a material medium for propagation.
Can be mechanical or electromagnetic in nature.	Purely mechanical wave.

Any 1 combination

f = ¹/_T T = 2(S)
Hence f = ¹/₂= 0.5Hz

1. Can travel for long distances as a beam without getting scattered.
2. It can be reflected by tiny particles like grains hence can defect them. ✓¹ Any 1
P = VI ✓¹
I = ^P/_V = 3000
240
= 12.5A✓¹
The fuse is not suitable since the appliance is drawing more current than the fuse rating ✓¹ the fuse will blow off.
His car gets charged by friction during the day. He then acts as earth wire when he step on the ground holding the metal handle.
1. 1. Vₚ = Nₚ
    Vₛ Nₛ
    
    800 = 2000
    Vₛ 150
    Vₛ = 800 x 150
    2000
    = 60V✓¹
  2. Power input = Power output ✓¹
    Iₚ = 1000
    800
    = 1.25A✓¹
  3. Iₛ = power output = 1000
    output voltage 60
    = 16.67A ✓¹
  4. Step-down transformer ✓¹
2. 1. - To minimize power loss.
    - Thick cables minimizes resistance.
  2. 2000 x 2 x 30 = 120kwh ✓¹
    1000
    75 x 10 x 30 = 22kwh
    1000
    
    1500 x 1 x 30 = 45kwh
    1000 total 189kwh ✓¹
    Cost 187 × 9.50
    = Ksh.1776.50 ✓¹
  3. No of units = 187
    Fuel levy 187 x 70/100= 130.90
    Standing charge = 200.00
    Total charge = 1776.50 + 330.90
    = Ksh.2107.40
1. 1. Increasing the number of turns in the coil.
  2. Increasing the size of current.
  3. Using a soft iron core
  4. Reducing the length of the core.
3. E = IR + Ir
  = 5 × 1.6 + 5r --- (i)
  E = 3.2 × 2.8 + 3.2r ---- (ii)
  Hence
  5 × 1.6 + 5r = 3.2 × 2.8 × 3.2r
  1.8r = 8.96 + 8
  1.8r = 0.96
  r = 0.96 = 0.53333
  1 .8
  E = 5 × 1.6 + 5 × 0.53
  = 8 + 2.65
  = 10.65V
4. ∫= RA / y✓①
  ✓①y = 10 x 7 x 10¯⁸
  1.1 x 10^-6
  70 /1.1 x 10^-2m
  = 63.6 × 10ˉ²m
  or
  63.6cm ✓①
5. P.d across R = p.d across 10Ω resistor. ✓①
  V + IR = 2 × 10 = 20V ✓①
1. 1. Long sight
  2. eye ball being too long
    focal length too short
2. It is the ability of the eye to focus the image on the retina
3. 1. ¹/_u + ¹/_v = ¹/_f
    ¹/_u + ¹/₄₅= ¹/₁₅
    ¹/_u =¹/₁₅- ¹/₄₅ = ²/₄₅
    U=⁴⁵/₂= 22.5cm
    Apparent depth =22.5cm
  2. n= real depth/apparent depth
    real depth=n x AD
    =⁴/₃ x ⁴⁵/₂
    =15x2
    =30cm.
    _gn_l =^1.4/_1.6 =sin ^45°/_Sinr
    sinr =1.6sin 45/1.4
    =0.742
    r = 53.0
4. 1. i = 45°

1. Increasing the surface area of the liquid. ✓①
2. Reducing the pressure on the liquid surface. ✓①
Heat gained by water = Heat lost by metal block
M_wC_w Ө_w = M_mC_m Ө_m ✓①
2 × 4200 × (50 – T₁) = 10 × 450 × 70 ✓①
50T1 = 10 x 450 x 70 = 37.5
2 x 4200
T1 = 50 – 37.5 = 12.5°C ✓①
Water has a high heat capacity hence can absorb a lot of heat ✓①
1. Increasing the pressure on the ice. ✓①
2. Adding impurities e.g. salt ✓①
As ether evaporates, it extra it’s the latent heat of vaporization from its surroundings hence the water is cooled. ✓①

Heat	Temperature
Form of energy which flows from a hotter to a cooler part of an object	Degree of hotness or coldness of an object measured on a given scale.
Measured in joules	Measured in Kelvin or °C.
Measured using a calorimeter	Measured using a thermometer.

Any two

Last…
1. 1. Up motion h1 = 40t – 5t² ✔1
    Down motion h2 = 5t²
    But h₁ + h₂ = 100m
    100 = 5t² + -5t² + 40t✔1
    t = ¹⁰⁰/₄₀ = 2.5 seconds ✔1
  2. hi = 40t – 5t²
    = (40 x 2.2) – 5 (2.5)2✔1
    = 100 – 31.25
    = 68.75m✔1 from the ground
2. 1. w = 2πf
    = 2 x ²²/₇ x 6✔
    = 37.7 radis✔
  2. a = rw²
    = 0.6 x (37.7²) ✔
    = 853.42 radis✔
  3. F = ma
    = 0.045 x 853.42✔
    = 38.4N ✔
  4. v = rw
    = 0.6 x 37.7
    = 22.62 m/s ✔