# Physics Paper 3 Questions and Answers - Cekenas Mock Exams 2022

QUESTIONS
Question 1

1. You are provided with the following apparatus:
• A boiling tube,
• Some dry sand
• A liquid in a beaker labeled L
• Half meter rule
• Vernier caliper (To be shared)
• A weighing balance (To be shared)
• Tissue paper
Proceed as follows:
1. Measure the length of the boiling tube using the vernier calipers.
h=……………….cm (1mrk)
2. Put a little amount of sand in the boiling tube and place it in the beaker which is almost filled with liquid L. Add sand little by little until the tube floats upright as shown in the figure bellow.
3. Measure the length d, part of the boiling tube which is above the liquid.
d=……………….cm (1mrk)
4. Determine the length t, of the boiling tube which is immersed in the liquid.
t=………………cm (1mrk)
5. Remove the boiling tube from the beaker, wipe it dry on the outside and measure its mass, including the sand inside.
m=……………….g (1mrk)
6. Measure the external diameter, D, of the boiling tube.
D=…………………..cm (1mrk)
7. Determine the external reading, R (1mrk)
R =………  +  ……..cm
8. Using the formula , determine  of the liquid (3mks)
2. You are provided with the following apparatus:
• One plane mirror.
• One rectangular glass block.
• One white plane paper.
• Soft board.
• A protector (student geometrical set).
• A piece of plastic.
• Four optical pins.
Proceed as follows
1. Place the glass block vertically on the white paper with its largest surface facing you. Draw the outline of the block and label it ABCD. Remove the block.
2. From point c measure angle y=30º and draw line CE as shown in the diagram.
3. From point B, fix a pin P1 at 2.5cm from B along BA and another pin P2 2.5cm from P1 and 10cm from point F on line AB. As shown in the diagram.
4. Replace the glass block and put the plane mirror vertically on line CE behind the glass block (fix it with plastacine). Arrange pins P3 and P4 to be in a straight with the image of P1 and P2 as seen through the glass block after reflection from the plane mirror. Draw a line P3P4 to meet the block at P as in the figure below.
5. Measure angle X and state its units (1mk)
X =……………………………………………………..
6. Given the equation Y= Y0 - 0.515X determine the value of y0. (2mks)
7. Find n from the formula n =       1
sin(90 - Yo)
3. You are provided with;
• A candle,
• A biconvex lens,
• A lens holder,
• A meter rule,
• A white screen.
Proceed as follows;
1. Arrange the lit candle and the white screen on the bench at a distance of 100cm from each other. Mount the meter rule on the bench as shown so that it’s zero mark coincides with point of the lit candle and 100cm mark coincide with the position of the screen.
2. Place the lens between the screen at a point near the candle. Move the lens systems together with its holder towards the screen until you observe a sharp magnified inverted image of the flame on the screen.
Record the distance U1 between the lens and the lit candle.
U1…………….cm (1mrk)
3. Move the lens system further towards the screen until you obtain another position where a sharp diminished inverted image of the flame is formed on the screen.
Record the new distance U2 between the lens and the candle.
U2=…………….cm (1mrk)
4. Determine the displacement d of the lens (1mrk)
d = U2 - U1
5. Determine Constant Ø given that Ø = 1 + m when m = 100 - U1  (3mks)
mU1                      U1

Question 2
You are provided with the following apparatus;

• Ammeter (0-1 A)
• Voltmeter (0-5V)
• Two dry cells
• One resistance wire fixed on a meter rule/mm scale.
• A switch
• Six connecting wires with crocodile clip.
• A cell holder

1. Set up a circuit and measure the potential difference M across the cells before connecting the circuit.
M =…………………………….    (1mk)
2. Arrange the circuit as shown below.
3. Keeping both crocodile clips attached on the resistance wire QZ for a length L=0.1m from Q, record corresponding values of current I (A) and voltage (V) in the table below.
Repeat the procedure from the other length L of L 0.2m, 0.3m, 0.4m, 0.5m, 0.6m, 0.7m and 0.8m.
 Length L(m) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Current I(A) Voltage V (V) P = V/I(Ω) 1/I(A-)
4. Draw a graph of 1/I against P (5mks)
5. Given that the Quantities are connected by the equation 1/= P/m x x/m
Determine the value of
1. m (4mks)
2. x (2mks)

CONFIDENTIAL
Each student will require;

Question one

• Boiling tube approx. 15.0cm tall and diameter 2.4±0.5cm
• Some dry sand
• Half meter rule
• Vernier calipers (to be shared)
• Weighing balance (At least one per room)
• A piece of tissue paper.
• A glass beaker (at least 600ml almost full of liquid L and labeled L)
(Liquid L is brine prepared with 1kg salt in 5 liters of water)
• A plane mirror.
• A rectangular glass block approximately 100mm×60mm×18mm.
• A plain white paper.
• Soft board.
• Protractor (Student geometrical set)
• A piece of plasticine.
• Four optical pins
• A lit candle
• A biconvex lens of f =15cm
• A lens holder
• A meter rule
• A white screen.

Question Two

1. Ammeter (0-1A)
2. Voltmeter (0-5V)
3. Two new size D cells.
4.  A cell holder.
5. A resistance wire fixed on a millimeter scale (SWG 31)
6. A switch.
7. Six connecting wire with crocodile clips.

## MARKING SCHEME

Question One

1.
1. h =14.8 ± 1.0cm
2. d = 4.3 ± 0.2cm
3. t = C.E of h-d -C.E/Exact
4. m = 51.10 ± 1.00g
5. D = 2.43±0.02cm 2d.p must
6. R = C.E(D/2)
7. C.S
C.E
4 s.f/ exact +unit
2.
1. x = 47º
2. yo= C.S
C.E 4 s.f or exact
3. C.S (4 sf/ exact)
3.
1. U1 = 20.0 ± 2.0
2. U= 80.5 ± 2.0cm
3. C.E of d (exact subtraction U1-U2)
4. Evaluation of M 4 sf or exact.
C.S of M
Evaluation of Ø 4 s.f or exact

Question Two

1. M = 3.0±0.1v

2.  Length L(m) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Current I(A) 0.50 0.41 0.36 0.35 0.27 0.25 0.23 0.20 Voltage V (V) 0.6 1.0 1.25 1.5 1.6 1.7 1.8 1.85 P = V/I(Ω) C.E 1/I(A-) C.E

3. A-1
S-1
P-2
C-1
4. m =   1
slope
x = C.S/C.E

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