# Physics Paper 3 Questions and Answers - Form 3 End Term 3 Exams 2023

INSTRUCTIONS TO CANDIDATES

• You are supposed to spend the first 15 minutes reading the whole paper carefully before commencing your work.
• Candidates are advised to record their observations as soon as they are made.
• Marks are given for observation actually made, their suitability, accuracy and the use made of them.

QUESTION 1

You are provided with the following apparatus

• A Metre rule
• A wire of length at least 100cm
• A retort stand, boss and clamp.
• A stop watch or stop clock
• A micrometer screw gauge
• An overflow can
• A beaker at least 50ml or more.
• A 50ml measuring cylinder
• Water in a 250ml beaker
• Two pieces of wood.
• Mass labelled m.
You are required to follow the following procedure
1.
1. Fill the overflow can with water to overflowing and then allow it to drain.
2. Immerse the mass m into the can. Collect the overflow in a beaker as shown below in the figure 1, below.

Figure 1
3. Using the measuring cylinder provided determine the volume V of the water collected in the beaker.
V = ______cm3 (1 mark)
4. Calculate I given that I = 106m    (Where m = 0.30 kg) (2 marks)
V
2. Set up the apparatus as shown in figure 2 below. Ensure that the wire is free of kinks and the end tied to the hook is firm and the hook does not move.

Figure 2
3. Adjust the length L, of the wire so that L = 70cm, Give the mass m, a slight twist such that when released it oscillates about the vertical axis as shown by the arrows in figure 2. Measure the time for twenty oscillations and record in Table 1.
4. Repeat the procedure in (c) above for other values of L, as shown in Table 1.
Complete the table. (6 marks)
Table 1
 Length L (cm) 70 60 50 40 30 20 Length L (m) Time for 20 oscillations(s) Period T(s) T2 (S2)
5. On the grid provided, plot the graph of T2 (S2) (y – axis) against L (m) (5 marks)

6. Measure the diameter d of the wire. (1 mark)
d = ………………………. metres
7.
1. Determine the slope of the graph. (2 marks)
2. Given that T2 = 32π2L where G is a constant, use the graph to determine the value of G. (3 marks)
Gd

QUESTION TWO

You are provided with the following:

• A rectangular glass block
• 4 optical pins
• A soft board
• A plain paper.
• A lens and a lens holder.
• A screen with cross wires
• A candle
• A metre rule.
• One cell and a cell holder
• Six connecting wires, two with crocodile clips
• A switch
• A resistor labeled, R
• An Ammeter
• A voltmeter

PART A

Proceed as follows:

1. Place the glass block on a sheet of paper fixed on the soft board with one of its longest face uppermost. Mark the outline ABCD as shown below.
Remove the glass block and draw a line EF to represent a ray of light making an angle of incidence I = 30° with the longest side BC of the block.
2. Fix pins P1 and P2 on the line EF. Replace the glass block and mark the emergent ray GH by viewing from side AD. Place pins P3 and P4 in line with images of P1 and P2.
Remove the glass block and the pins and draw the ray EFGH.
3. Draw the normal at G.

Figure 3
4.
1. Measure angle B    (1 mark)
2. Measure the lateral displacement d.
d = ……………… cm (1 mark)
5. Given that k = Sin 30°
Sin B
Calculate the value of k. (2 mark)
6. What quantity does k represent? (1 mark)
7. Arrange the lightened candle, the lens and the screen as shown in figure 4. Adjust the position of the screen until a sharp inverted image of the candle is formed on the screen.

Figure 4
Measure the image distance, v.
v = …………………………… cm (1mark)
8. Determine the focal length of the lens using the formula f  uv       (3 marks)
u + v
9. Now arrange the lighted candle, the screen with cross wires and the lens as shown in figure 5. Ensure that the centre of the lens, the cross-wires, and the candle flame lie on the same horizontal line. The candle flames should be placed close to the cross-wires for better illumination.

Figure 5
10. Adjust the position of the lens until a sharp image of the cross-wire is formed on the screen next to the cross wires. (Hint: You have to rotate the lens slightly about a vertical axis so that the image of the cross-wires falls on the screen next to the cross-wires and not on the cross-wires.)
Measure the distance d, between the lens and the screen.
d = ----------- cm (1mark)
11. Determine the values of: L and X:
1. L =    df       (2 marks)
f − d
2. X =    L  + 1 (2marks)
2f
PART B
Proceed as follows:
12. Set up the apparatus as shown below.

While the switch is open, record the reading E of the voltmeter
E = …………… volts (1mark)
13. Close the switch and record the reading, V, of the voltmeter and I the reading of the ammeter
1. V = ………… volts (1mark)
2. I = ……………amperes (1mark)
14. Given that E = V + Ir, determine the value of r
r…………… volts (3 marks)

MARKING SCHEME

QUESTION 1

1. a)   iii)    V = 45cm3 ✔                                   (1mark)
I = 106 x 0.30 Substitution          ✔ (1mark)
45
iv)    6,666.7kg/m3                                  ✔ (1mark)

d) Table 1

 Length L (cm) 70 60 50 40 30 20 Length L (m) 0.7 0.6 0.5 0.4 0.3 0.2 Time for 20 oscillations(s) 61.01 56.08 51.36 46.06 39.81 32.8 Period T(s) 3.051 2.804 2.568 2.303 1.991 1.64 T2 (S2) 9.309 7.862 6.595 5.304 3.96 2.69

• Correct conversion of length L in M ✔ (1mark)
• Time for 20 oscillation ✔    (½mk for each value within range)                (maximum of 3mks)
• Correct evaluation of period ✔ (1mark)
• Correct evaluation of T2 ✔ (1mark)

e)    Axes: Labelled with units ✔ (1mark)
Scale: Simple and uniform ✔ (1mark)
Plotting: Each correctly plotted point ✔✔ ( ½ mark) to a max of 2mks (2 marks)
(4 correctly plotted points within 1 small square)
Line: Passing through at least 3 points correctly plotted ✔ (1mark)

f) d = 0.34 x 10-3
= 3.4 x 10-4m ✔ (1mark)
g) i) ∆T2 = 8.6 − 2.0√ = 0.1320s2/m√ (2 marks)
∆L      65 −15
(deny ½ for no units and fully for wrong units)
ii)
gradient = 32π2√ ≡ G =     32π2     =          32π√       = 7,037,151√ (3 marks)

QUESTION TWO

d)  i)   B = 19 ± 1°                  (To the nearest degree) (1 mark)
ii)   d = 1.7 ± 0.2 cm           (1 dp) (1mark)

e) K = Sin 30°
Sin B (correct substitution of B)√,
(correct evaluation for k), √ (2 marks)
NB No unit for k

f)  K = refractive index (1mark)

g) V = 34.3 cm ±0.5 cm   1 d.p (1 mark)

h) f =   uv  = 30×34.3√ = 16.00cm√√ 4s.f(correct answer and correct units) (3 marks)
u+v     30+34.3

j) d = 7.5 cm ± 0.5 cm 1d.p (1 mark)

k)  i)  L=  df   = 7.5×16√ = 120 = 12.63cm√ 4 sf (2 marks)
f − d   16-7.5       9.5
ii) X =  L + 1 ≡ 12.63 + 1√ = 1.395cm√ (2 marks)
2f           2(16)

PART B

i) E = 1.5V √ ± 0.1 (1mark)

m)  i)  V = 1.14V√ ± 0.1v 1mark
ii) I = 0.04A√ ± 0.1A (1mark)

n) E = V + 1r
1.5 = 1.14 + 0.04 r √correct substitution
1.5 – 1.14 = 0.04r
0.36 = 0.04r

r =  0.36 = 9Ω√√ correct evaluation with correct units (3 marks)
0.04

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