# Physics Paper 3 Questions and Answers with Confidential - Kassu Joint Mock Examination 2021

INSTRUCTIONS TO CANDIDATES

• Write your name and index number in the spaces provided.
• Mathematical tables and non-programmable calculators may be used.
• This paper consists of three questions.
• Attempt all the questions in the spaces provided.
• ALLOW working MUST be clearly shown.

QUESTION ONE
Apparatus

• stopwatch
• 250ml beaker
• Rubber bung
• Thermometer
• Bunsen burner
• Tripod
• Gauze
• Retort stand and clamp
• Hot water

Figure 2.

Procedure

1.
1. Measure and record the ambient temperature, TA =…………………..ºC (1 mark)
2. Fill an empty beaker with exactly 150ml of hot water (check the side scale of the beaker)
3. Set up the apparatus as shown in figure 2. Ensure the thermometer is about 2cm above the bottom of the beaker.
4. Record the initial highest temperature of water TH=………………….. ºC (1 mark)
2. Start the stopwatch and time for every 2.0 minutes the temperature T of water. Record the temperature in Table 2 for 20 minutes
 Time (t) in minutes 2 4 6 8 10 12 14 16 18 20 Temperature (T) in ºC (T-TA)ºC Log10(T-TA) (2 d.p)
(6 mark)
3. Plot a graph of Log10(T-TA) against time (5 mark)
4. From the graph determine:
1. The Slope S (3marks)
………………………………………………………………………………………………………………………………………………………………………………………
2. The cooling constant , K of water given S=-0.4343K (2 mark)
5. Given that the specific heat capacity of water is 4.2J/g/0C determine the heat lost when the water cools to the temperature of the surrounding ( 2 mark)
1. PART A
You are provided with the following apparatus :
• One resistor labelled R = 40Ω
• A wire labelled W mounted on milliameter scale
• A wire labelled S mounted on a milliameter scale
• One dry cell and a cell holder
• One jockey
• one centre zero galvanometer
• Eight connecting wires, four with crocodile clips at both ends
• A micrometer screw gauge
• A switch

Proceed as follows

1. Determine the average diameter D, of the wire labelled W using the micrometer screws gauge provided.
D1 = ............................................................ mm (½ mark)
D2 = ............................................................. mm (½ mark)
D = D1 + D2 (in cm)
2 (1 mark)
2. Set up the apparatus as shown in the circuit diagram in figure 3 below.
Use the crocodile clips to fix length L, of wire labelled S at 50cm from the end connected to the galvanometer G.
3. Close the switch and use the jockey to touch one end of the wire W, and then the other end. The deflections on the galvanometer should be in opposite directions, if not check the circuit. Adjust the positions of the jockey along the wire W until there is no deflection in the galvanometer. Record the value of x and y.
x = ..................................................................... cm (½ mark)
y = .................................................................... cm (½ mark)
4. Record for other values of L in table 3 below
 L (cm) 45 40 35 30 25 20 X (cm) Y (cm) y/x (3 d.p)
(4 marks)
5.
1. Plot a graph of y/x (y-axis) against L. (5 marks)
2. Determine the slope, m of the graph. (2 marks)
3. Given that K = 100D, determine the value of K. (2 marks)

PART B

1. You are provided with a lens P a lens holder a white screen and half metre rule.

Procedure
1. Set the apparatus as shown in figure 4 below. Focus a sharp image of a distant object on the screen (e.g window frame). The object should be 10cm away.The object should be at least 10cm away.
1. Measure the distance x in cm between the lens and the screen at which a sharp image is obtained repeat this two times, using different objects and record your readings in table 4 below.
 Object Distance X, (cm) 1 2
(2 marks)
1. Calculate the average value of x (1 mark)
……………………
2. What is the physical significance of the result obtained in (iii) above? (1 mark)
……………………….

PHYSICS CONFIDENTIAL
QUESTION ONE

• stopwatch
• 250ml beaker
• Rubber bung
• Thermometer
• 150 ml of boiling water
• Tripod
• Gauze
• Retort stand and clamp
• Hot water

QUESTION 2
PART A

• One resistor labelled R = 40Ω
• A wire labelled W mounted on millimetre scale (32 gauge)
• A wire labelled S mounted on a millimetre scale (28 gauge)
• One dry cell and a cell holder
• One jockey
• One centre zero galvanometer
• Eight connecting wires, four with crocodile clips at both ends
• A micrometer screw gauge
• A switch

PART B

• Lens and a lens holder (f=10cm)
• Half metre rule
• White screen

## MARKING SCHEME

QUESTION ONE
Apparatus

• stopwatch
• 250ml beaker
• Rubber bung
• Thermometer
• Bunsen burner
• Tripod
• Gauze
• Retort stand and clamp
• Hot water

Figure 2.

Procedure

1.
1. Measure and record the ambient temperature, TA = 4ºC (1 mark)
2. Fill an empty beaker with exactly 150ml of hot water (check the side scale of the beaker)
3. Set up the apparatus as shown in figure 2. Ensure the thermometer is about 2cm above the bottom of the beaker.
4. Record the initial highest temperature of water TH= 83 ºC (1 mark)
2. Start the stopwatch and time for every 2.0 minutes the temperature T of water. Record the temperature in Table 2 for 20 minutes
 Time (t) in minutes 2 4 6 8 10 12 14 16 18 20 Temperature (T) in ºC 72 71 67 63 60 58 56 54 52 51 (T-TA)ºC 48 47 43 39 36 34 32 30 28 27 Log10(T-TA) (2 d.p) 1.68 1.67 1.63 1.59 1.56 1.53 1.51 1.48 1.45 1.43
(6 mark)
3. Plot a graph of Log10(T-TA) against time (5 mark)
4. From the graph determine:
1. The Slope S (3marks)
G =Δy =1.65 - 1.45
Δx       4 - 18
2. The cooling constant , K of water given S=-0.4343K (2 mark)
-0.01429 = -0.4343K
K = 0.03289
5. Given that the specific heat capacity of water is 4.2J/g/ºC determine the heat lost when the water cools to the temperature of the surrounding ( 2 mark)
H = Mcθ
M = 150cm3 x gm3
= 150g
H = 0.15 x 4200 x 59
= 37.170J
1. PART A
You are provided with the following apparatus :
• One resistor labelled R = 40Ω
• A wire labelled W mounted on milliameter scale
• A wire labelled S mounted on a milliameter scale
• One dry cell and a cell holder
• One jockey
• one centre zero galvanometer
• Eight connecting wires, four with crocodile clips at both ends
• A micrometer screw gauge
• A switch

Proceed as follows

1. Determine the average diameter D, of the wire labelled W using the micrometer screws gauge provided.
D1 = 0.30 mm (½ mark)
D2 = 0.30 mm (½ mark)
D = D1 + D2 (in cm)
2 (1 mark)
0.30 + 0.3.0
2
= 0.30mm
2. Set up the apparatus as shown in the circuit diagram in figure 3 below.
Use the crocodile clips to fix length L, of wire labelled S at 50cm from the end connected to the galvanometer G.
3. Close the switch and use the jockey to touch one end of the wire W, and then the other end. The deflections on the galvanometer should be in opposite directions, if not check the circuit. Adjust the positions of the jockey along the wire W until there is no deflection in the galvanometer. Record the value of x and y.
x = 88.3 cm (½ mark)
y = 11.7 cm (½ mark)
4. Record for other values of L in table 3 below
 L (cm) 45 40 35 30 25 20 X (cm) 92.6 93.5 94.5 95 96 96.5 Y (cm) 7.4 6.5 5.5 5 4 3.5 y/x (3 d.p) 0.08 0.07 0.058 0.053 0.042 0.036
(4 marks)
5.
1. Plot a graph of y/x (y-axis) against L. (5 marks)
2. Determine the slope, m of the graph. (2 marks)
G =Δy =(8 - 0) x 10-2 = -0.08
Δx        45 - 0              45
1.778 x 10-3 cm
3. Given that K = 100D, determine the value of K. (2 marks)
K = 100 x 0.30
10
= 30mm

PART B

1. You are provided with a lens P a lens holder a white screen and half metre rule.

Procedure
1. Set the apparatus as shown in figure 4 below. Focus a sharp image of a distant object on the screen (e.g window frame). The object should be 10cm away.The object should be at least 10cm away.
1. Measure the distance x in cm between the lens and the screen at which a sharp image is obtained repeat this two times, using different objects and record your readings in table 4 below.
 Object Distance X, (cm) 1 10.0 2 10.0
(2 marks)
1. Calculate the average value of x (1 mark)
10 +10 = 10cm
2
2. What is the physical significance of the result obtained in (iii) above? (1 mark)
Total length

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