# Physics Paper 3 Questions and Answers - Form 4 End Term 1 Exams 2021

PHYSICS
FORM 4
END TERM EXAMS
TERM 1 2021
PAPER 3
(PRACTICAL)
TIME 2 ½hrs

INSTRUCTIONS

• This paper consists of 2 Questions
• Answer all the questions in these sections
• Mathematical tables and calculators may be used.
• Working must be clearly shown
• Record observations as soon as they are made.
1. Question 1
1. PART A
You are provided with the following:
• A 200ml beaker
• A thermometer
• A complete retort stand
• 100ml measuring cylinder
• A calorimeter with a stirrer
• Some water
• A heat source
• A 100g mass
• A balance

1. Proceed as follows:
Fill the 200ml beaker to about half its volume with water. Clamp the thermometer and lower it into the water, ensuring that its bulb does not touch the base or sides of the beaker. Tie the 100g mass with the thread securely and gently lower it into the water as shown below; 2. Weigh the mass of the empty calorimeter and record it.
Mass (Mc)= _________________g (½ mark)
3. Measure 90ml of water and gently transfer it into the calorimeter. Measure and record the temperature of the water in the calorimeter.
θ1 = ________________ºc (½ mark)
4. Determine the mass of water in the calorimeter by weighing both the water and the calorimeter.
Mw = ________________ g (1mark)
5. When the water with the 100g mass has started to boiling note and record the temperature θs of the solid.
θs = ________________ ºc (½ mark)
6. Quickly transfer the hot solid into the water in the calorimeter and cover it. Ensure that the calorimeter is well lagged. Stir gently and note the final steady temperature of the mixture.
θ2 = ________________ºc (½ mark)
7. Given that MsCss2)=(McCc+MwCw)(θ21)
Where:
Ms =Mass of the solid
Mc =Mass of the calorimeter
Mw =Mass of water in the calorimeter
Cw =Specific heat capacity of water = 4200J/Kg/K
Cc =Specific heat capacity of the calorimeter =400J/Kg.
Find the value of Cs the specific heat capacity of the solid. (3marks)
2. PART B
You are provided with:
• Two dry cells size D
• One voltmeter
• One ammeter
• Six connecting wires with crocodile clips
• A potentiometer
• A switch
• A cell holder to hold two cells
• A bulb and bulb holder
1. Set up the circuit as shown below: 1. Close the switch S and adjust the potentiometer till the bulb lights brightest. Record the ammeter and voltmeter readings
I = ______________________A (1 mark)
V = ______________________V (1 mark)
2. By adjusting the potentiometer, obtain the corresponding readings of current for the values of the voltmeter readings given in the table below.
 Voltmeter Reading V (V) 0.1 0.3 0.5 0.8 1.0 1.2 1.5 1.7 Ammeter Reading I(A)
(4marks)
3.
1. Plot a graph of voltmeter reading (V) against ammeter reading (A) (5 marks)
2. From your graph, determine the resistance of the bulb when the voltmeter reading is 0.5V. (3marks)
2. You are provided with the following;
• An optical bench or metre rule
• A convex lens and lens holder
• A candle stick
• Screen I with a hole and crosswires at its centre
• Screen II
• A wooden block
• A vernier calipers (to be shared)
• Weighing balance (to be shared)
1. PART A
Proceed as follows:
1. By focussing on a distant object e.g a window, obtain an estimate for the focal length of the convex lens.
Focal length = _____________________cm (1 mark)
2. Place the screen I at the zero mark of the metre rule on the optical bench (It should remain at this point throughout the experiment). Then place screen II at the distance L = 45cm. Light the candle and stand it in position to light up the cross wires. Put the convex lens on the lens holder and adjust its position between the two screens such that you obtain a sharp magnified image of the cross wires on screen II. (See figure 1) Figure 1
3. Read the mark for the position of the lens holder on the metre and hence record the distance in table 1.
4. Repeat the procedure above for other values of L and complete table 1.
 L(cm) U(cm) (L-U)(cm) P=U(L-U)cm2 45 50 60 70 90 100
(5 marks)
5. On a grid , plot a graph of P (y-axis) against L (5 marks)
6. Determine the slope of the graph. (3 marks)
2. PART B
1. Take the wooden block and using the vernier callipers provided measure and record the;
Length = ___________________ cm = ________________m (1 mark)
Width = ___________________ cm = ________________m (1 mark)
Thickness = ___________________ cm = ________________ m (1 mark)
2. Take the same wooden block in (g) above and using the weighing balance determine its mass
Mass = ___________________g = ________________kg (1 mark)
3. Using the values obtained in (g) and (h) above, determine the density of the wooden block giving
the answer in SI units. (2 marks)

CONFIDENTIAL

1. The information contained in this paper is to enable the head of school and the teacher in charge of Physics to make adequate preparations for this year’s Physics practical examination. NO ONE ELSE should have access to this paper or acquire knowledge of its contents. Great care MUST be taken to ensure that the information herein does not reach the candidates either directly or indirectly.
2. The Physics teacher is not expected to perform the experiments.
3. The apparatus required by each candidate for the Physics practical examination are set out on page 2. It is expected that the ordinary apparatus of a Physics laboratory will be available. The Physics teacher should note that it is his/ her responsibility to ensure that each apparatus acquired for this examination agrees with the specification on pages 2.
4. The question paper will NOT be opened in advance.
5. Teachers are reminded that electronic calculators may be allowed in the examination rooms.
N.B
Any use of apparatus other than the ones specified may lead to candidates being penalized.

Physics teachers should ensure each student is provided with the following.

1. QUESTION 1
1. PART A
• A source of heat
• A cotton thread 50cm long
• A thermometer
• A complete retort stand
• 100ml measuring cylinder
• A calorimeter with a stirrer (N.B: teachers are advised to improvise where copper calorimeters are not available)
• 200ml beaker
• Some water
• A 100g mass
• A weighing balance (Accuracy (0.1g), to be shared)

2. PART B
• Two dry cells, size D
• One voltmeter
• One ammeter
• Six connecting wires with crocodile clips
• A potentiometer 50Ω (One used in K.C.S.E 2012)
• A switch
• A cell holder that can hold two cells
• A 2.5V, 0.2A bulb and a bulb holder

2. QUESTION 2
• Optical bench or metre rule
• A wooden block(5.0 cm × 3.5cm × 1.0cm)
• Convex lens of focal length 10 cm
• Lens holder
• Candle
• Screen I with a hole and cross wires at the centre
• Screen II (white)
• A vernier callipers(to be shared)
• Weighing balance(to be shared)
N.B:
• This information should be handled with strict confidentiality
• The teacher can improvise a calorimeter where necessary by using a beaker which is well lagged. ## MARKING SCHEME

1. Question 1
1. PART A
1.
2. Mc = 60g  (work with the students value)
3. θ1=27 ± 1ºC
4. Mw = 90g
5. θs = 98ºC or 100ºC
6. θ2 = 34ºC ± 1ºC
7. Cs = ([(0.06 ×400)×7]+(0.09 ×4200 ×7))/(0.1 ×66)
= 2.814/6.6
= 426.36 J/kgk
2. PART B
1.

2.  Voltmeter Reading V (V) 0.1 0.3 0.5 0.8 1 1.2 1.5 1.7 Ammeter Reading I(A) 0.08 0.14 0.16 0.18 0.19 0.2 0.23 0.25
½ mk each correct value. Maximum 4 marks
3.
1. Graph 2. Slope = (1-0)/(0.2-0.12) (correct substitution)
= 1/0.08
= 12.5 Ω  (Correct evaluation with correct unit)
2.
1. PART A
1. Focal length estimate = (9.5 – 10.5)cm
2.
3.

4.  L(cm) U(cm) (L-U)(cm) P=U(L-U)cm2 45 16.0 29.0 464.0 50 14.3 35.7 510.5 60 13.5 46.5 627.8 70 12.4 57.6 714.2 90 12.2 77.8 949.2 100 12.0 88.0 1056.0

5. 6. Taking points (40, 410) and (89, 940)
(Check indication on the graph)
Slope = (940-410)/(89-40)
= 108 cm
(9.0 – 11.0)cm
2. PART B
1. Length = 5.14 cm  = 0.0514m
Width = 3.42cm  = 0.0342 m
Thickness/ height = 1.04cm = 0.0104m
Total 3 marks
Values should be recorded to correct degree of accuracy
2. Mass = 15.8g = 0.0158kg
Total 1 mark
3.  Volume = 0.0514 x 0.0342 x 0.0104
= 1.828 x 10-5 m3
Density = mass/volume
= 0.0158/(1.828 × 10-5)
= (864.24 kg / m-3)/(Range ±10)

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