# PHYSICS PAPER 3 - 2019 KCSE KASSU JOINT MOCK EXAMS (QUESTIONS AND ANSWERS)

QUESTION 1

1. You are provided with the following apparatus
• Two beakers.
• A complete retold stand.
• Funnel
• Cotton wool.
• Stop watch.
• A burette with a tap (50cm3).
• 100ml measuring cylinder.

Proceed as follows:
1. Set the apparatus as follows:

1. Support the burrete on a result as shown above
2. Close the tap of the burrete and fill it with water to the brim
3. Transfer the water to the 100ml measuring cylinder and record the volume of the water
2. Fill the burrette with water up to the 0cm3 mark. Drain this water into 100ml measuring cylinder and record its volume V2
3. Fill the burrete with water to the brim. Finally open the tap at once and start the stop watch simultaneously. Obtain the time, t taken for the level of water to reach X=10cm3
4. Refill the burette with water. Finally open the tap at once and start the stopwatch simultaneously. Obtain the time taken for the level of water to reach x = 20cm3
5. Repeat the procedure for other values of the burette readings.
6. Record the volume drained and the corresponding time in the table below.(9marks)
 Burette reading Volume of water drained Time t (s) Log10 V 10 20 30 40 45 50
7. Plot the graph of log10v (vertical axis) against time t.    (5mks)
Using your graph, calculate the value for b and n from the equation.   (3mark)
2. QUESTION 2
You are provided with the following apparatus:
• Resistance wire fitted on a scale labelled MN
• Switch
• Voltmeter (0.3v) or (0.5v)
• Ammeter (0.1A)
• Two dry cells
• Six connecting wires
1. Set up the apparatus as shown in the figure below
2. Remove the crocodile clip from the resistance wire MN and close the switch. Record the voltmeter reading.
3. Attach the crocodile clip to the resistance wire such that L=10cm
4. Record the voltmeter and ammeter reading in the table below.
5. Repeat the procedure in (iii) and (iv) for L= 20 cm, 30 cm, 40 cm, 50cm, 60 cm, 70cm and 80 cm.
6. Complete the table below.(9mks)
 Length L (cm) 10 20 30 50 80 Current I (A) p.d V (V) Y-V V/Y-V V/I = R (αΎ¨)
7. Plot the graph of, vertical axis against R  (5mks)
1. Determine the slope, m of the graph  (2mks)
2. The graph is given by the equation
3. Determine the value of m and d       (3mks)

## MARKING SCHEME

1. QUESTION 1
You are provided with the following apparatus
• Two beakers.
• A complete retold stand.
• Funnel
• Cotton wool.
• Stop watch.
• A burette with a tap (50cm3).
• 100ml measuring cylinder.
Proceed as follows:
1. Set the apparatus as follows:
2. Support the burrete on a result as shown above
3. Close the tap of the burrete and fill it with water to the brim
4. Transfer the water to the 100ml measuring cylinder and record the volume of the water
Volume V1 = 65cm  (1mk)
5. Fill the burrette with water up to the 0cm3 mark. Drain this water into 100ml measuring cylinder and record its volume V2
V2 = 53cm3 (1mk)
The excess water above the zero mark is given by
V0 = V1 – V2
V0 = 65 – 53 = 12cm  (1mk)

(This volume should be added to the final volume of the burette reading when water has been drained)
6. Fill the burrete with water to the brim. Finally open the tap at once and start the stop watch simultaneously. Obtain the time, t taken for the level of water to reach X=10cm3
Volume drained = (V0+10) cm3
7. Refill the burette with water. Finally open the tap at once and start the stopwatch simultaneously. Obtain the time taken for the level of water to reach x = 20cm3
Volume drained = (V0+20) cm3
8. Repeat the procedure for other values of the burette readings.
9. Record the volume drained and the corresponding time in the table below.(9marks)
 Burette reading Volume of water drained Time t (s) Log10 V 10 22 15.90 1.3424 20 32 23.29 1.5051 30 42 33.15 1.6232 40 52 44.12 1.7160 45 57 49.50 1.7559 50 62 59.28 1.7924
10. Plot the graph of log10v (vertical axis) against time t.    (5mks)

Slope =1.88-1.3/64-0
=0.58/64
= 0.009s-1
11. Using your graph, calculate the value for b and n from the equation.   (3mark)
Log10 V = 4.2t/b+n
n= the vertical intercept
n = 1.28
Slope = 4.2/b
b = 4.2/slope

b = 4.2/0.009
= 466.755
2. QUESTION 2
1. You are provided with the following apparatus:
• Resistance wire fitted on a scale labelled MN
• Switch
• Voltmeter (0.3v) or (0.5v)
• Ammeter (0.1A)
• Two dry cells
• Six connecting wires
1. Set up the apparatus as shown in the figure below
2. Remove the crocodile clip from the resistance wire MN and close the switch. Record the voltmeter reading.
Y = 2.7 V    (1mk)
3. Attach the crocodile clip to the resistance wire such that L=10cm.
4. Record the voltmeter and ammeter reading in the table below.
5. Repeat the procedure in (iii) and (iv) for L= 20 cm, 30 cm, 40 cm, 50cm, 60 cm, 70cm and 80 cm.
6. Complete the table below.(9mks)
 Length L (cm) 10 20 30 50 80 Current I (A) 0.86 0.48 0.43 0.255 0.205 p.d V (V) 2.1 2.3 2.4 2.5 2.6 Y-V 0.6 0.4 0.3 0.2 0.1 V/Y-V 3.5 5.75 8 12.5 26 V/I = R (αΎ¨) 2.4419 4.7917 5.5814 9.8039 12.6829
At least 3 correct readings row 1 and 2 - (2mks)
4-5 correct reading row 1 & 2 – (3 mks)
Row 3 & 4 all correct - (1mk)
7. Plot the graph of, vertical axis against R  (5mks)

1. Determine the slope, m of the graph  (2mks)
2. The graph is given by the equation
3. Determine the value of m and d       (3mks)

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