# Physics Paper 3 - 2021 KCSE Prediction Questions and Answers Set 1

### Instructions to Candidates

1. Answer all questions on this question paper
2. You are supposed to spend the first 15 minutes allowed for this paper reading the whole paper carefully before commencing your work and confirming your apparatus.
3. Marks are given for a clear record of the observations actually made, (or their suitability and accuracy  and or the use made of them)
4. Candidates are advised to record observations as soon as they are made.
5. Mathematical tables or electrical calculators may be used
6. Candidates should answer all the questions in English

QUESTION 1

You are provided with the following

• Water in a beaker
• Complete retort stand
• Two clamps
• 100ml measuring cylinder
• Boiling tube
• Meter rule
• Beam balance(can be shared)
• Vernier calipers (can be shared

Proceed as follows

1. Using the vernier calipers, measure the internal diameter of the boiling tube (1mk)
2. Measure the length H, of the boiling tube                                                                  (1mk
3. Measure the mass of the boiling tube using the beam balance                 (1mk)
4. Clamp the boiling tube vertically with its base resting on a flat surface as shown, Use the second clamp to clamp the meter rule beside the boiling tube.
5. Measure 10ml of water and pour into the boiling tube. Measure the height h, of the water.
6. Keep adding water in small amounts in the boiling tube and complete the table below
 Volume of water in cm3/ml Height, h (cm) 10 20 35 45 50 65
On the grid provided, plot a graph of volume V(cm3) of water (y-axis) against height h(cm)     (5mks)
7. From the graph determine the slope, (3mks)
8. Wind the cotton thread ten times round the boiling tube, pushing the windings very close together, the turns should not overlap on each other.

Unwind the thread and measure the length L of the thread.                                                                                    (1mk)
9. Calculate the volume V,of the glass material which the boiling tube is made of, given that
(2mks)
10. Calculate the density d, of the glass material of the boiling tube                                                                    (2mks)

QUESTION 2

PART A

You are provided with the following

• A meter rule
• Convex lens
• A candle
• Len’s holder
• Cross wither mounted on a cardboard
• A white screen

Proceed as follows:-

1. Set up the apparatus as shown
2. Starting with U=30cm vary the position of the screen S until a sharp image of the cross wire is observed on the screen. Measure and record the value of the image distance V.
3. Repeat the experiment above for other values of U, and complete the table below                                                                                           (6mks)
 U(cm) 30 35 40 45 50 55 V(cm) M= V/U
1. Plot a graph of M against V (5mks)
2. Determine the slope of the graph (3mk)
3. The equation of the graph is given by M=v/f-1. Use your graph to obtain the value

PART B
You are provided with the following apparatus:

• One cell and a cell holder
• Six connecting wires, two with crocodile clips
• A switch
• A 10 carbon resistor labledded R
• An Ammeter
• A voltmeter

Proceed as follows

1. Set up the apparatus as shown below.

Record the reading E of the voltmeter     (1mk)
2. Close the switch and record the reading, V, of the voltmeter and I the reading of the ammeter
3. Given that E = v + V + 1r, determine the value of r

## MARKING SCHEME

QUESTION 1

1. 2.24cm 1
H=14.9cm
2.
1. 24.7g
 Volume of water in cm3/ml Height h (cm) 10 20 35 45 50 65 2.7 5.1 6.4 8.8 10.0 13.6
Graph paper Each ½mk     total 3mks                                                                                                     (3mks)
2. Gradient = 4.231cm2                without unit ½mk
3. L= 86cm
4. H= 14.9
= 149 5.9168 – 4.231
= 14.9
= 25.11842
5. Density
= 0.9833g/cm3

QUESTION 2

 u(cm) 30 35 40 45 50 55 v(cm) 15 14 13.5 12.9 12.5 12.0 1mk each Max 5 points m =v/u 0.5 0.4 3375 1mk all correct

6mks

1. Graph paper :
Axes- well labelled quantity and units                                                                            (1mk)
Scale – uniform, simple and accommodative                                                                (1mk)
Plotting – exact points or to 1small square mk each max of 4                                                                                                             (2mks)
Line – should pass through majority of points with positive gradient                     (1mk)
2. Slope =0.1cm-1
= 0.1
f = 10cm

PART B

1.
1. E =1.5V (1mk)
2. V = 1.14
I= 0.04A 0.1 (1mk)
3. E = V + 1V
1.5 = 1.14 + 0.048 r
1.5 – 1.14 = 0.048
0.36 = 0.04r
R = 9

CONFIDENTIAL

Question 1

1. Complete retort stand with two clamps
2. Some water in a beaker (100m2)
3. 100ml measuring cylinder
4. Boiling tube
6. Meter rule
7. Beam balance (can be shared)
8. Vermier calipers (can be shared)

Question 2

1. Meter rule
2. Convex lens of focal length 10cm
3. A cande
4. Lens holder
5. Cross wire mounted on a cardboard
6. A white screen
7. One cell
8. Cell holder (one cell)
9. A switch
10. Six connecting wires, at least two with crocodile clips.
11. 10Ω carbon resistor (label it R)
12. Ammeter
13. Volt meter

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