# Physics Paper 3 Questions and Answers - Maranda High School Mock Exams 2023

Instructions to Candidates

• Answer ALL the questions in the spaces provided in the question paper
• You are supposed to spend the first 15 minutes of the 2 ½ hours allowed for this paper reading the whole paper carefully before commencing your work.
• Marks are given for a clear record of the observations actually made.
• Non-programmable silent electronic calculators and KNEC Mathematical tables may be used except where stated otherwise.

QUESTION 1

You are provided with the following: -

• a resistor labelled Ro
• a mounted wire AB of kength 100cm, (nichrome SWG 32)
• an ammeter 0-1A,
• a voltmeter 0 - 5V,
• a switch
• six connecting wires,
• two new dry cells,
• a cell holder

Proceed as follows:

1.
1. Set the circuit shown in the figure 1.

Figure 1
2. With the switch closed, measure and record the current thorugh the wire AB and the voltage across it.
I = .........................................  A  (1  mark)
V = ........................................  V   (1 mark)
3. Determine the T resistance per centimetre.     (2 marks)
2.
1. Set up the apparatus as shown in figure 2
2. Clip the wire Ab at the length L = 15cm and close the switch. Read and record the Current 1 in table 1
3. .Clip the wire AB at other lengths, L shown in the table 1. Read and record the currents 1 in table 1.
4. Complete table 1 by determining the values of 1/I and resistance R    (5 marks)
Table 1
 Length, L (cm) 15 30 45 60 75 90 Current, I (A) 1/I (A−1) Resistance R = T × L(Ω)
3.
1. On the grid provided, plot a graph of 1/I (A−1) against resistance, R(Ω)   (5 marks)

QUESTION 2

PART A

You are provided with the following apparatus:

• Metre rule
• A complete retort stand
• Two masses, a 50g and 20g mass
• Water in a beaker
• Liquid X in a beaker
1. Suspend the metre rule so that it balances at its centre of gravity G. Read and record the value of G.…………………………………………………………………… (1 mark)
2. Suspend the 50g mass at a distance d=10cm, then suspend the 20g mass and adjust its position such that the metre rule is balanced as shown in the figure 2

Figure 2
3. Record the distance distance d1
d1…………………………………………………. cm (1 mark)
4. While maintaining the distance d , immerse the the 50g mass completely in water, as shown in the figure 3.

Figure 3
5. Adjust the position of the 20g mass to balance the metre rule again. Record the new distance d2
d2………………………………………………………….. cm (1 mark)
6. Using the results obtained above, calculate the value of W1, weight of the 50g mass in water.    (2 marks)
7. Determine the upthrust U1 on the 50g mass in water. (2 marks)
8. Repeat steps (d), (e) and (f) but now the 50g is totally immersed in liquid X as shown in the figure 4.

Figure 4
9. Using the results obtained above, calculate the value of W2, weight of the 50g mass in liquid X. (2 marks)
10. Determine the upthrust U2 on the 50g mass in liquid X. (2 marks)
11. Given that ρL = U × ρw where ρw = 1000kgm−3 . Calculate PL  (2 marks)
U1

QUESTION 3

PART B

You are provided with the following apparatus:-

• A metre rule.
• Stop watch.
• Stand, clamp and boss.
• Spring.
• Two pieces of wood.
• A beam balance or electronic balance (to be shared)
• Mass labelled M.

Proceed as follows:Hang the spring vertically by clamping one end as shown in figure 5.

1.               Figure 5
2. Measure the length, Lo of the unloaded spring, and record below.
Lo = ……………………………………………… cm (1 mark)
3. Hang the mass M given from the lower end of the spring. Measure the length, of the loaded spring.
L1 = ………………………………….. cm (1 mark)
4. Find the value of
L = L1 − L0 = ……………………………………..cm (1 mark)
5. Using the beam balance, determine the mass, M of the object.
M = …………………………………………kg (1 mark)
6. Hang the mass M from the lower end of the spring. Displace it by a small vertical distance and release so that the spring makes vertical oscillations. Measure and record, time for the number of oscillations given in the table 2.
7. Complete table 2. (3 marks)
 Oscillations, N 10 Time in seconds, t (s) Q = (N + 10t)s             10

### MARKING SCHEME

QUESTION 1

You are provided with the following: -

• a resistor labelled Ro
• a mounted wire AB of kength 100cm, (nichrome SWG 32)
• an ammeter 0-1A,
• a voltmeter 0 - 5V,
• a switch
• six connecting wires,
• two new dry cells,
• a cell holder

Proceed as follows:

1.
1. Set the circuit shown in the figure 1.

Figure 1
2. With the switch closed, measure and record the current thorugh the wire AB and the voltage across it.
I = .........0.12 − 0.24 2dp (closed range)  ✓1  ................................  A  (1  mark)
V = .......2.0 − 2.6  1dp (closed range)   ✓1 .................................  V   (1 mark)
3. Determine the T resistance per centimetre.     (2 marks)
R = V/l =  2.6  ÷ 100cm
0.24/cm
T = 0.1083Ω
2.
1. Set up the apparatus as shown in figure 2
2. Clip the wire Ab at the length L = 15cm and close the switch. Read and record the Current 1 in table 1
3. .Clip the wire AB at other lengths, L shown in the table 1. Read and record the currents 1 in table 1.
4. Complete table 1 by determining the values of 1/I and resistance R    (5 marks)
Table 1
 Length, L (cm) 15 30 45 60 75 90 Current, I (A) 0.3 0.28 0.26 0.24 0.22 0.2 1/I (A−1) 3.333 3.571 3.846 4.167 4.545 5 Resistance R = T × L(Ω) 1.6245 3.249 4.874 6.498 8.123 9.747
3.
1. On the grid provided, plot a graph of 1/I (A−1) against resistance, R(Ω)   (5 marks)

QUESTION 2

PART A

You are provided with the following apparatus:

• Metre rule
• A complete retort stand
• Two masses, a 50g and 20g mass
• Water in a beaker
• Liquid X in a beaker
1. Suspend the metre rule so that it balances at its centre of gravity G. Read and record the value of
G.……………50 ± 1.0cm 1d.p a must……………………………………………………… (1 mark)
2. Suspend the 50g mass at a distance d=10cm, then suspend the 20g mass and adjust its position such that the metre rule is balanced as shown in the figure 2

Figure 2
3. Record the distance distance d1
d1…………25.0 ± 1.0  1dp a must………………………………. cm (1 mark)
4. While maintaining the distance d , immerse the the 50g mass completely in water, as shown in the figure 3.

Figure 3
5. Adjust the position of the 20g mass to balance the metre rule again. Record the new distance d2
d2………19.0 ± 1.0 1 dp a must……………………………….. cm (1 mark)
6. Using the results obtained above, calculate the value of W1, weight of the 50g mass in water.    (2 marks)
W1d = Wd2
W1 × 10cm = 0.2N × 19.0cm     Correct substitution in the principle of moments
W1 = 0.38N ✓1 Correct answer 4sgf or exact * (ignore units)
7. Determine the upthrust U1 on the 50g mass in water. (2 marks)
U1 =   50   × 10 − 0.38  ✓½ Correct substitution
1000
0. 5 − 0.38   ✓½ Correct evaluation
U1 = 0.12N  ✓1 Correct answer  4sgf or exact  *(ignore units)
8. Repeat steps (d), (e) and (f) but now the 50g is totally immersed in liquid X as shown in the figure 4.

Figure 4
9. Using the results obtained above, calculate the value of W2, weight of the 50g mass in liquid X. (2 marks)
d3 = 21.0cm ± 1.0cm
W2 × 0.0m = 0.2N × 0.21m   Correct substituion in principle of moments
W2 = 0.42N  ✓1 Correct answer 4sgfor exact *Ignore units
10. Determine the upthrust U2 on the 50g mass in liquid X. (2 marks)
U2 =   50    × 10 − 0.42      ✓ ½ correct substitution
1000                ✓  ½ correct evaluation
= 0.08N  ✓  1 correct answer   (4sgf or exact) * Ignore units)
11. Given that ρL = U × ρw where ρw = 1000kgm−3 . Calculate PL  (2 marks)
U1
ρL = 0.08N × 1000  ✓ ½ correct substitution
0.12N              ✓ ½ correct evaluation
666.67 kg/m3           ✓1 correct answer with correct unit  (4sgf or exact)
Missing unit - deny ½
Wrong unit- penalize fully.

QUESTION 3

PART B

You are provided with the following apparatus:-

• A metre rule.
• Stop watch.
• Stand, clamp and boss.
• Spring.
• Two pieces of wood.
• A beam balance or electronic balance (to be shared)
• Mass labelled M.

Proceed as follows:

1. Hang the spring vertically by clamping one end as shown in figure 5.

Figure 5
2. Measure the length, Lo of the unloaded spring, and record below.
Lo = …………15.0 (students value, 1dp a must)…………………………………… cm (1 mark)
3. Hang the mass M given from the lower end of the spring. Measure the length, of the loaded spring.
L1 = …………36.0 (Students value, 1dp a must ……………………….. cm (1 mark)
4. Find the value of
L = L1 − L0 = …36.0 − 15.0 = 21.0 (Correct substraction of students value)…………………………………..cm (1 mark)
5. Using the beam balance, determine the mass, M of the object.
M = ……0.08 − 0.11 (closed range) correct evaluation of students value……………………………………kg (1 mark)
6. Hang the mass M from the lower end of the spring. Displace it by a small vertical distance and release so that the spring makes vertical oscillations. Measure and record, time for the number of oscillations given in the table 2.
7. Complete table 2. (3 marks)
 Oscillations, N 10 Time in seconds, t (s) (8.00 − 12.00s) Q = (N + 10t)s             10 (8.00 + 10 × 8.00)             10      = 8.8
2dp a must closed range  ✓1
* working must be shown
*Correct substitution  ½
* Correct evaluation  ½
* Correct answer to 4sgf or exact ✓1 Ignore unit

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