# Physics Paper 3 Questions and Answers - Lugari Constituency Joint Pre Mock Exams 2023

Instructions to candidates

You are provided with the following:

• A watch glass
• A small piece of plasticine
• A marble
• A stop watch
• Vernier calipers
• Triangular glass prism
• Four Optical pins
• Some cello tape
• A soft board
• A plain sheet of paper
• An electronic balance (for sharing)
1. Record the mass of the marble.  ………………………………………….m (1mk)
1. Place the watch glass flat on the table with a small piece of plasticine to fix it firmly to the bench at the one place it touches. Release the marble from one end of the watch glass and time 10 complete oscillations with a stop watch. Repeat this three times.

 1 Time for 10 oscillation Periodic time T(s) 2 3
(2mks)
Find the average periodic time (2mk)
2. Measure the diameter of the marble with vernier calipers and hence find its radius.
Diameter   (1mk)
3. Determine the volume of the marble given that V = 4       (2MKS)
3πr3
4. Calculate the radius of curvature of the watch glass R from the formular
R − r = 5gT2          (2MKS)
7(2π)
Where g=9.8m/s2 , =3.142
5. Determine the density of the marble (2mks)

PART B
6. Fix the plain sheet of paper on the soft board using some cello tape. Place the triangular prism on the paper and trace its outline on the sheet of paper. Remove the prism and use a ruler to extend the three side of the outline.
Measure angle A and the length l
A= ……(1MK)
l……(1MK)
NB: The plain sheet of paper must be submitted together with the question paper.
7. At a point about a third way along one side of the outline from angle A, draw a normal.
8. raw a line at angle i=40° to the normal. Stick two pins P1 and P2 vertically on this line as shown below.
Place the prism accurately on the outline. By viewing through the opposite side, stick two other pins P3 and P4 vertically such that they are in line with the two images of pins P1 and P2.
Measure angle D
9. For two other values of angle I shown in the table 2 locate and measure the corresponding angles of deviation. Complete table 2 (2mks)
Table 2
 I 40° 50° 60° D
10. Determine the average value Dm of D (1MK)
11.      (2MKS)

QUESTION II

You are provided with the following:

• A wire W mounted on a mm scale
• 2 dry cells and a cell holder
• A voltmeter
• Five connecting wires (some with crocodile clips)
• A Switch
• Proceed as follows:
1. Set up the apparatus as shown in the figure below:

E = …volts (1mk)
2. Set up the apparatus as shown in the figure below. Use the crocodile clip to fix the length L of wire W at 10cm.

3. Close the switch. Record the voltmeter reading (V) in the table.
4. Adjust the length L to 20cm and repeat step (c) above. Repeat for other values L in the table. Complete the table below:

 L (cm) V (Cm) E−V (VOLTS) V                 ( E−V) 10 20 30 40 50 60
5.
1. Plot a graph of V(E-V) against L (5mks)
2. Determine the slope of the graph (3mks)
6. The equation of the graph is given by V    = K1L + K2 determine the value of :
(E-V)
1. K1 (2MKS)
2. K2 (2MKS)
7. Given that 4K2r = 10, where r is the internal resistance of the cells. Determine the value of r. (2mks)

MARKING SCHEME

You are provided with the following:

• A watch glass
• A small piece of plasticine
• A marble
• A stop watch
• Vernier calipers
• Triangular glass prism
• Four Optical pins
• Some cello tape
• A soft board
• A plain sheet of paper
• An electronic balance (for sharing)
Record the mass of the marble….m (1mk)
1. Place the watch glass flat on the table with a small piece of plasticine to fix it firmly to the bench at the one place it touches. Release the marble from one end of the watch glass and time 10 complete oscillations with a stop watch. Repeat this three times.

 Time for 10 oscillation Periodic time T(s) 1 0.70 2 0.70 3 0.70
(2mks)
Find the average periodic time   (2mk)
0.70+0.70+0.70 = 0.70 seconds
3
2. Measure the diameter of the marble with vernier calipers and hence find its radius.
• Diameter…1.70cm     (1mk)
3. Determine the volume of the marble given that V =   4
3πr3 (2MKS)
Correct substitution   (1mk)
Correct evaluation to exact or at least 4sgf (1mk)
4. Calculate the radius of curvature of the watch glass R from the formular
R − r =  5gT2  (2MKS)
7(2π)2
Where g = 9.8m/s2 , π = 3.142
Correct substitution  (1mk)
Correct evaluation to exact or at least 4sgf (1mk)
5. Determine the density of the marble (2mks)
Correct substitution (1mk)
Correct evaluation to exact or at least 4sgf (1mk)

PART B

1. Fix the plain sheet of paper on the soft board using some cello tape. Place the triangular prism on the paper and trace its outline on the sheet of paper. Remove the prism and use a ruler to extend the three side of the outline.

Measure angle A and the length l
• A = 60°      (1MK)
• l = 4.6cm   (1MK)
NB: The plain sheet of paper must be submitted together with the question paper.
2. At a point about a third way along one side of the outline from angle A, draw a normal.
3. Draw a line at angle i = 40° to the normal. Stick two pins P1 and P2 vertically on this line as shown below.

Place the prism accurately on the outline. By viewing through the opposite side, stick two other pins P3 and P4 vertically such that they are in line with the two images of pins P1 and P2. Measure angle D
1. For two other values of angle I shown in the table 2 locate and measure the corresponding angles of deviation. Complete table 2 (2mks)
Table 2

 I 40° 50° 60° D 41° 39° 40°

41°+39°+40° = 400
3
Correct substitution 1mk
Correct evaluation to exact or at least 4sgf 1mk
4. Determine the average value Dm of D (1MK)
5. (2MKS)
Correct substitution  (1mk)
Correct evaluation to exact or at least 4sgf (1mk)

QUESTION II

You are provided with the following:

• A wire W mounted on a mm scale
• 2 dry cells and a cell holder
• A voltmeter
• Five connecting wires (some with crocodile clips)
• A Switch
Proceed as follows:
1. Set up the apparatus as shown in the figure below:

E = 3.00±0.20  volts    (1mk)
2. Set up the apparatus as shown in the figure below. Use the crocodile clip to fix the length L of wire W at 10cm.
3. Close the switch. Record the voltmeter reading (V) in the table.
4. Adjust the length L to 20cm and repeat step (c) above. Repeat for other values L in the table. Complete the table below: (5mks)

 L (cm) V (Cm) E−V (VOLTS) V                 ( E−V) 10 1.70 1.30 20 1.90 1.10 30 2.00 1.00 40 2.10 0.90 50 2.20 0.80 60 2.30 0.70

V ±0.2 ½ each up to 3mksevaluation of  V   , correct evaluation to exact or 4sgf (1mk)
(E-V)
E − V, 1MK
5.
1. Plot a graph of  V    against L (5mks)
(E-V)
Axis – well labeled axis with correct unit and correct physical quantity
Plotting - ½ mk for each correctly plotted value within one small square up to a max of   (2mks)
Scale- 1mk for uniform and simple scale
Straight line with a positive gradient passing through at least three correctly plotted points (1mk)
2. Determine the slope of the graph (3mks)
Correct change in y-coordinates 1mk
Correct change in x coordinate 1mk
Correct evaluation of slope to exact or 4sfg 1mk
6. The equation of the graph is given by  V    = K1L + K2 determine the value of :
(E-V)
1. K1            (2MKS)
• Substitution (½ mk)
2. K2            (2MKS)
• K2 = y-intercept (1mk)
• Substitution (1/2 mk)
• Correct evaluation to exact or 4sgf.(1/2 mk)
7. Given that 4K2r = 10, where r is the internal resistance of the cells. Determine the value of r. (2mks)
Correct substitution 1mk
Correct evaluation to exact or at least 4sgf 1mk

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