# Physics Paper 3 Questions and Answers with Confidential - Kapsabet Mock Exams 2021/2022

INSTRUCTIONS TO CANDIDATES

• Write your name, school and index number in the spaces provided above.
• Sign and write the date of the examination in the spaces provided above.
• You are not allowed to start working with the apparatus for the first 15 minutes of the 2½ hours allowed for this paper. This time is
• to enable you read the question paper and make sure you have all the apparatus you may need.
• Marks are given for a clear record of the observations actually made, for their suitability and accuracy and the use made of them.
• Candidates are advised to record their observations as soon as they are made.
• Mathematical tables and electronic calculators may be used in calculations.

Candidates should check the question paper to ensure that all pages are printed as indicated and no questions are missing.

1. You are provided with the following;
• A candle
• A white screen
• A metre rule
• A lens
• A lens holder
• A piece of plasticine.
Proceed as follows:
1. Arrange the apparatus as shown below.
2. Adjust the distance of the lens from the screen until a well-focused image of a very distant object like a tree, is seen on the screen. Record the distance between the screen and the lens as d.
d = _________________________________ cm (1 mark)
d = _________________________________ m (1 mark)
3. Now place the lens at the midpoint of the metre rule.
(It will remain at this point throughout the entire experiment) Arrange the screen and lit candle as shown below.

Mark the point A and B each of which a distance ‘d’ from the lens.
4. Place the lit candle at point d, 30cm from B. Adjust the position of the screen until a sharp image appears on it. The screen is at C. Measure BD and AC and record them as x and y respectively in the table below.
 BD = x (cm) AC = y (cm) 1/y (cm-1) 30 25 20 15 10
5. Repeat the procedure in (d) above for other values of x in the table and complete it. (6 marks)
6.
1. Draw a graph 1/y (y-axis) against x. (5 marks)
2. Determine the slope S of the graph. (3 marks)
3. Calculate the value of m given that
m = √1/s (2 marks)
4. Comment on values of m and d. (2 marks)

1. You are provided with the following:
• Clamp, boss and stand
• Optical pin fixed on a piece of cork.
• Copper wire of length 15cm
• Protractor
• Stop watch

Proceed as follows:

1. Bend the wire in the middle so that the angle formed is 200.
2. Set-up the apparatus as shown in the diagram below.
3.
1. Displace the wire horizontally and allow it to swing freely. Record time for 10 complete oscillations.
t = _______________________ seconds (1 mark)
2. Calculate frequency, f at time in (i) above. (1 mark)
4. Repeat the procedure above (c) for other given angles on the table below.
 Angle θº Time for 10 oscillation t (s) Frequency, f = t/10 f2(Hz)2 Cos(θ/2) 20º 40º 60º 80º 100º 120º
(7 marks)
5. On the grid provided, plot a graph of f2 (y axis) against Cos[θº/2] (5 marks)
6. Find the gradient of the graph. (3 marks)
7. The equation of the graph is f2 =150K/2L Cos θ/2 determine the value of constant K if L is the total length of the wire in centimeters. (3 marks)

CONFIDENTIAL
INSTRUCTIONS TO SCHOOLS

1. The information contained in this paper is to enable the head of school and the teacher in charge of Physics to make adequate preparations for this year’s Physics practical examination. NO ONE ELSE should have access to this paper or acquire knowledge of its contents. Great care MUST be taken to ensure that the information herein does not reach the candidates either directly or indirectly.
2. The Physics teacher is Not expected to perform the experiments.
3. The apparatus required by each candidate for the Physics practical examination are set out on page 2.
It is expected that the ordinary apparatus of a Physics laboratory will be available.
The Physics teacher should note that it is his/ her responsibility to ensure that each apparatus acquired for this examination agrees with the specification on pages 2.
4. The question paper will NOT be opened in advance.
5. Teachers are reminded that electronic calculators may be allowed in the examination rooms.
N.B
Any use of apparatus other than the ones specified may lead to candidates being penalized.

Each candidate requires the following;
Question 1

• A candle
• A white screen
• A metre rule
• A convex lens of focal length 20cm
• A lens holder
• A piece of plasticine

Question 2

• A clamp, boss and retort stand
• Optical pin fixed on a piece of a cork
• A copper wire of length 15 cm and diameter 1.0mm
• A protractor
• A stop watch

## MARKING SCHEME

1. QUESTION ONE
Part A

1. d = 20.0 ± 1 cm
d = 0.02 ± 0.01m

2.  BD= Xcm AC = Y (cm) 1/y (cm-1) 3025201510 16.017.520.025.528.0 0.06260.05710.05000.03920.0357 4 marks for values within the range. Each value ± 1 cm 2 marks for correct calculation
(6 marks)
3.
1.
2. 0.63-0.50)cm-1
30-20 (cm)
= 0.13/10
= 0.013cm-2 (Answer to have the correct units)
3. M = √1/0.013
= 8.771cm (Answer with units)
4.
• M is approximately half of d
• d is approximately the focal length of the lens
2. QUESTION TWO
1.
1. t = 4.51± 2 seconds
2. 4.51/10 = 0.451Hz

2.  Angle θº Time for 10 oscillation t (s) Frequency, f = t/10 f2(Hz)2 Cos(θ/2) 20º 4.51 0.451 0.2034 0.9848 40º 4.94 0.494 0.2440 0.9397 60º 5.06 0.506 0.2560 0.8660 80º 5.50 0.550 0.3025 0.7660 100º 6.00 0.640 0.3600 0.6428 120º 6.20 range ±1 sec 0.620 0.3844 0.5000 3 mks 1 mk for correct calculation 1 mk for correct calculation 2 mk(for correct calculation
3.

4. = (0.36-0.20)Hz2
0.64-0.98
= 0.16
- 0.34
= - 0.4706Hz2 (Answer with units)
5. f2 = 150k/4πL Cos θ/2
Slope = 150k/4πL
L = 150 ×15
4π2
=   2250
39.478
= 56.994

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