## Physics Paper 3 Questions, Answers and Confidential - KCSE 2022 Mock Exams Set 1

INSTRUCTIONS:

• Answer all the questions in this paper
• You are supposed to spend the first 15 minutes of the 2 1/2 hours allowed for this paper reading the whole paper carefully before starting your work.
• Marks are given for clear record of the observations made, their suitability and accuracy and the use made of them.
• Candidates are advised to record observations as soon as they are made
• Mathematical table and electronic calculators may be used.
• The earth’s gravitational pull, g=10N kg -1

For Examiner’s use only:

 QUESTION TOTAL MARKS CANDIDATE’S SCORE 1 20 2 20 GRAND TOTAL 40

### QUESTIONS

QUESTION ONE
You are provided with the following apparatus:

• Two new size ‘D’ dry-cells
• switch
• milli-ammeter
• voltmeter (0-3V)
• two enameled copper rods
• rheostat ( Ω)
• eight connecting wires with at-least 4 fitted with crocodile clips
• Micrometer screw-gauge (to be shared)
• 50 ml beaker (labelled, A)
• 75 ml of distilled water (labelled, B)
• solid X
• Measuring cylinder
• Thermometer
• Glass-rod for stirrer
• Sand-paper

Proceed as follows:

1. Measure the temperature of the distilled water in beaker, B
Temperature, θ = ............................ (1 mark)
2. Place the provided solid X into the beaker labelled, A. measure 50 ml of the distilled water and gently pour it into beaker A and stir gently until all the solid X is dissolved to form solution, C.
3. Measure the diameter, d of one of the copper rods.
1. diameter, d = ............................ m (1 mark)
2. determine the cross-section area, A of the copper rod (2 marks)
A =
4. Using the sand paper, remove the insulating coating at the both ends of each of the copper rods. Now set-up the apparatus as shown in figure 1 below. Figure 1
5. With the help of the rheostat, set the current value to 30 mA and measure its corresponding voltage, V.
V = ............................ (1 mark)
6. Repeat the above procedure for the values of current indicated in the table, 1 below and note their corresponding voltages. Complete the table. (5 marks)
Table 1
 Current, I (mA) 30 40 50 60 70 Current, (A) Voltage, V
7. In the grid provided, plot a graph of voltage (y-axis) against current (A) (X-axis) (5 marks) 8. Determine the slope, S of the graph (3 marks)
9. The voltage and current are related by the equation: V - bI/A =0
Determine the value of b. (2 marks)
b= .............................................

QUESTION TWO
You are provided with the following apparatus:

• Complete retort-stand (clamp, boss and stand)
• Half metre-rule
• Metre-rule
• G-clamp
• Office pin
• Four 100g masses (or its equivalent)
• Some celotape
• Vernier calipers (to be shared)
• One 50g mass
• Knife-edge

PART A
Proceed as follows:

1. Arrange the apparatus as shown in figure 2, below. Ensure the 10 cm mark of the half metre-rule is at the edge of the table and firmly held by the G-clamp while the pin (pointer) is at the 90 cm mark on the scale of the metre-rule. (The clamp should not be removed for the entire duration of carrying-out this experiment) 2. Suspend one 100 g mass at the 49.5 cm mark and record the new pointer reading, P1
P1=............................... (1 mark)
3. Continue adding the load in 100 g steps, each time recording the pointer position. Ensure that the half metre-rule is not overloaded.
4. Determine the amount of sagging, X and complete the table, 2 below. (6 marks)
Table 2
 Mass (g) Load (N) Pointer position (cm) Amount of sagging, X (m) 100 200 300 400
PART B
Procedure
5. Use the Vernier calipers to determine the width, a and breadth, b of the half metre-rule Width, a = ......................... cm (1 mark)
breadth, b = ........................ cm (1 mark)
6. Using a loop of thread suspend the 50g mass at the 49.5cm mark on the half-metre rule.
7. With the 50g mass fixed at that position adjust the position of the half-metre rule on the knife edge until it balances horizontally as shown in figure 4. 8. At the balance position, read off the length x and y and record in table 3.
9. Using the values of x and y obtained in ‘h’ above, determine the weight, W of the half metre-rule (3 marks)
W = ................................
10. Move the suspended mass 2cm towards the centre of the rule and repeat parts (g) and (h) to obtain other values of x and y so as to complete table 3. (4 marks)
Table 3
 Position of the mass of 50g X (cm) Y (cm) 49.5 cm mark 47.5 cm mark 45.5 cm mark 43.5 cm mark 41.5 cm mark
11. Given that quantity, P is given by: ; determine the value of P (3 marks)
12. State the significance of the quantity, P (1 mark)

### MARKING SCHEME

INSTRUCTION TO THE TEACHER:

This marking scheme may not be the final draft. The author acknowledges that there could be other perspectives of facts and so the teacher concerned is highly encouraged to adapt it accordingly.

QUESTION ONE
You are provided with the following apparatus:

• Two new size ‘D’ dry-cells
• switch
• milli-ammeter
• voltmeter (0-3V)
• two enameled copper rods
• rheostat ( Ω)
• eight connecting wires with at-least 4 fitted with crocodile clips
• Micrometer screw-gauge (to be shared)
• 50 ml beaker (labelled, A)
• 75 ml of distilled water (labelled, B)
• solid X
• Measuring cylinder
• Thermometer
• Glass-rod for stirrer
• Sand-paper

Proceed as follows:

1. Measure the temperature of the distilled water in beaker, B
Temperature, θ = ...25ºc   range ; ± 10 ºc ..... (1 mark)
2. Place the provided solid X into the beaker labelled, A. measure 50 ml of the distilled water and gently pour it into beaker A and stir gently until all the solid X is dissolved to form solution, C.
3. Measure the diameter, d of one of the copper rods.
1. diameter, d = ..0.0110  range ; ± 0.001m  (1 mark)
2. determine the cross-section area, A of the copper rod (2 marks)
A = πr2 = 3.142 x (0.0110/2)2
= 0.00009505 m2
= 9.505 x 10-5 m2
4. Using the sand paper, remove the insulating coating at the both ends of each of the copper rods. Now set-up the apparatus as shown in figure 1 below. Figure 1
5. With the help of the rheostat, set the current value to 30 mA and measure its corresponding voltage, V.
V = 0.70 V (1 mark)
6. Repeat the above procedure for the values of current indicated in the table, 1 below and note their corresponding voltages. Complete the table. (5 marks)
Table 1
 Current, I (mA) 30 40 50 60 70 Current, (A) 0.03 0.04 0.05 0.06 0.07 1 max Voltage, V± 0.1 v 0.7 0.9 1.2 1.5 1.8 4 max
7. In the grid provided, plot a graph of voltage (y-axis) against current (A) (X-axis) (5 marks) 8. Determine the slope, S of the graph (3 marks)
slope = V/I
1.65 - 0.75    = 0.9
0.065 - 0.035    0.03
= 30 Ω
correct evaluation with units
deny 1/2 for no units and full for wrong units
9. The voltage and current are related by the equation: V - bI/A =0
Determine the value of b. (2 marks)
b= b/A = slope = 30
b = 9.505 x 10-5 x 30
∴ b = 2.8515 x 10-3  Ω m2
correct evaluation with units
deny 1/2 for no units and fully for wrong units

QUESTION TWO
You are provided with the following apparatus:

• Complete retort-stand (clamp, boss and stand)
• Half metre-rule
• Metre-rule
• G-clamp
• Office pin
• Four 100g masses (or its equivalent)
• Some celotape
• Vernier calipers (to be shared)
• One 50g mass
• Knife-edge

PART A
Proceed as follows:

1. Arrange the apparatus as shown in figure 2, below. Ensure the 10 cm mark of the half metre-rule is at the edge of the table and firmly held by the G-clamp while the pin (pointer) is at the 90 cm mark on the scale of the metre-rule. (The clamp should not be removed for the entire duration of carrying-out this experiment) 2. Suspend one 100 g mass at the 49.5 cm mark and record the new pointer reading, P1
P1=..90.7 cm  1 d.p a must (1 mark)  range ; ± 0.2 cm
3. Continue adding the load in 100 g steps, each time recording the pointer position. Ensure that the half metre-rule is not overloaded.
4. Determine the amount of sagging, X and complete the table, 2 below. (6 marks)
Table 2
 Mass (g) Load (N) Pointer position (cm) Amount of sagging, X (m) 100 1 90.7 0.007 200 2 91.5 0.015 300 3 92.5 0.025 400 4 93.4 0.034 all correct  1mark 4 max all correct 1 max
PART B
Procedure
5. Use the Vernier calipers to determine the width, a and breadth, b of the half metre-rule Width, a = ..2.59.. cm (1 mark)  range ; ± 0.2 cm
breadth, b = .0.51.. cm (1 mark)  range ; ± 0.2 cm
6. Using a loop of thread suspend the 50g mass at the 49.5cm mark on the half-metre rule.
7. With the 50g mass fixed at that position adjust the position of the half-metre rule on the knife edge until it balances horizontally as shown in figure 4. 8. At the balance position, read off the length x and y and record in table 3.
9. Using the values of x and y obtained in ‘h’ above, determine the weight, W of the half metre-rule (3 marks)
W = ................................
At equilibrium ; sum of clockwise moment = sum of anti-clockwise moment
0.5 x 0.105 = w x 0.14
∴ w = 0.375
w = 0.375 N
correct evaluation with units
10. Move the suspended mass 2cm towards the centre of the rule and repeat parts (g) and (h) to obtain other values of x and y so as to complete table 3. (4 marks)
Table 3
 Position of the mass of 50g X (cm) Y (cm) range ; ± 0.2 cm range ; ± 0.2 cm 49.5 cm mark 10.5 39.0 47.5 cm mark 9.5 38.0 45.5 cm mark 8.7 36.8 43.5 cm mark 7.8 35.7 41.5 cm mark 7.0 34.5 2 max 2 max
11. Given that quantity, P is given by: ; determine the value of P (3 marks)
p   =            0.375
10(2.59 x 0.51 x 10-5)
= 2,838.9 kg/m3
12. State the significance of the quantity, P (1 mark)
density

### CONFIDENTIAL

INSTRUCTION TO THE PHYSICS TEACHER:
The physics teacher should plan with school management to ensure availability of the following apparatus for the learner to carry-out this practical examination.
Each candidate is expected to be provided with the following apparatus:
QUESTION ONE
• A milli-ammeter
• A volt-meter (0-3V)
• A switch
• Two enameled copper rods (each 10 cm long and about 0.10mm thick)
• Eight connecting wires with at least 4 fitted with crocodile clips
• Glass stirrer
• A micrometer screw-gauge (may be shared)
• 50 ml plastic beaker (labelled A)
• 75 ml of distilled water (beaker labelled B)
• 8g of solid copper II sulphate (crystal) labelled solid X
• Measuring cylinder
• Thermometer
• Sand paper
QUESTION TWO
• Complete retort-stand (clamp, boss and stand)
• Half metre-rule (wooden)
• Metre-rule (wooden)
• G-clamp (laboratory size clamp)
• Office pin (should be fixed at one end of the half metre-rule to act as a pointer on the scale)
• Four 100g masses (or its equivalent)
• Some celotape
• Vernier calipers (to be shared)
• One 50g mass with a hook
• Knife-edge (at least 15 cm high)
• Knife-edge (about 10 cm high)

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