# PHYSICS Paper 3 Confidential-Questions and Answers

Oct 24, 2022

## GET THE KCSE PREDICTION PHYSICS P3 MARKING SCHEMES HERE

Bunyore

QUESTION ONE

Every student should be provided with the following:

– A lens holder

-Convex lens of (focal length 15.0 cm + 1cm)

– A candle

– A white screen

– A metre rule

-A Equilateral triangular glass prism of side 3.7cm

-A plain sheet of paper

-A soft board

-4optical pins /thumbs

-4  paper pins

-A watch glass of (diameter 10.0cm + 1cm)

-A piece of plasticine about 20g

-A marble of (diameter 1.60 cm+ 0.50cm)

-A Stopwatch-An electronic balance (to be shared)

– Vernier calipers (to be shared)

– Geometrical set

QUESTION TWO

–     An ammeter (1 A)

–     A voltmeter (3 V or 5 V)

–     A variable resistor of 100Ω

–     A 10Ω carbon resistor

–     A piece of resistance wire (SWG 30) 50cm long

–     Two New Size D dry cells

–     A cell holder

–     A switch

–     Seven connecting wires of 4 should have crocodile clips both ends and 3 with crocodile clip on one end

## PHYSICS Paper 3 Confidential-Questions and Answers

QUESTION 1

PART A

You are provided with the following:

-A watch glass

-A piece of plasticine

-A marble

-A Stopwatch

-An electronic balance (to be shared)

– Vernier calipers (to be shared)

– Geometrical set

Proceed as follows:

(a) Measure the mass, m of the marble.

m = …………………………g                                                                       (1/2mark)

b) Place the watch glass on the table. Cut the plasticine into two pieces and use them to hold the watch glass firmly on the table as shown in Figure 1.

c). Release the marble from one end of the watch glass and time 5 complete oscillation with the stopwatch. Repeat this one more time.

d) Record your values in the Table 1                                                             (11/2 marks)

Table 1

e) Find the average periodic time T                                                               (1mark)

f) (i)Measure the diameter of the marble with the Vernier calipers, hence find its radius

Diameter, d = …………………                                                                     (1mark)

(ii)Determine the volume of the marble given that V=πr3                   where π=3.142           (1mark)

(iii)Calculate the radius of the curvature  of the watch glass R from  the formula R – r  =

Where g=10m/s2 and π=3.142                                                                      (1mark)

PART B

You are provided with the following:

•      A glass prism

•      A plain sheet of paper

•      A soft board

•      4 optical pins

•      2 Thumb tacks

Proceed as follows:

g) (i)Firmly fix the plain sheet of paper on the soft board using the thumb tacks and place the prism at the centre of the paper. Trace the outline of the prism using a pencil.

(ii)Remove the prism from the outline and label the vertices of the outline L, M and N as shown in Figure 2

Measure Angle LMN and length, Ɩ using a ruler

Angle LMN = ………………………                                                 (1mark)

Length, Ɩ = …………………………                                                  (1mark)

iii) On the side ML mark a point and draw the normal at that point. Measure an angle T, 60° from the line LM and draw a line along this angle as shown in Figure 3.

iv). Replace the prism on the outline and fix pins P1 and P2 on the 60° line at a distance of 3cm from each other. View the images of the pins P1 and P2 through side MN and fix P3 and P4 so that they appear to be on straight line with the images of P1 and P2.

v). Remove the prism and the pins and draw a line to pass through the holes made by pins P3 and P4. Extend the line into the outline as shown in figure 3 above. Also extend the 60° line so that the two lines cross each other at point O. Determine angle D and record it in the Table 2

h). (i)Repeat the procedure and complete the Table 2                                   (2 1/2marks)

Table 2

(ii) Determine the average value Dm of D                                                      (1mark)

iii) Determine the constant kfor the glass prism from the formula               (2marks)

PART C

You are provided with the following:

• A lens holder

• Convex lens

• A candle

• A white screen

• A metre rule

Proceed as follows:

i) Set up the apparatus as shown in Figure 4

(j) Starting with u = 30 cm, adjust the position of the screen to obtain a sharp image of the candle flame. Record the value of v in Table 3.

(k)(i) Repeat the procedure in (i) for u = 30 cm. Complete Table 3              (3marks)

Table 3

(ii) Given that the focal length f of the lens satisfies the equation f, determine the average value of the focal length, f.                                                                                (2 marks)

QUESTION 2

You are provided with the following:

–     An ammeter (1 A)

–     A voltmeter (3 V or 5 V)

–     A variable resistor

–     A 10Ω carbon resistor

–     A piece of resistance wire

–     Two new dry cells

–     A cell holder

–     A switch

–     Seven connecting wires

Proceed as follows:

a) Take the resistant wire and coil it around the biro pen to make a coil.

b) Set up the apparatus as shown Figure 5 below such that the 10Ω carbon resistor and the coil are in parallel connection.

c) Close the switch and the adjust the variable resistor such that the ammeter read a current of I1=0.08A and record the corresponding voltmeter reading V1

i) V1 =…………………                                                                                 (1mark)

ii) Calculate resistance                                                                     (1mark)

d) Repeat (c) above for current of I2 = 0.16A and record the corresponding voltmeter reading V2

i) V2 =…………………                                                                                 (1mark)

ii) Calculate resistance                                                                     (1mark)

e) Find the average value of resistance R                                                       (1mark)

f) Determine the resistance, C of the coil                                                       (2marks)

g) Now set up the apparatus as shown in Figure 6 below such that the voltmeter is connected across the cells, 10Ω carbon resistor and the coil are in parallel connection.

h) Close the switch and the adjust the variable resistor such that the ammeter reads a current of 0.04A and note the corresponding voltmeter reading. Record the value in the Table 4 below.

i) Repeat (h) above for other values of current and voltage and complete the Table 4 below

(4marks)         Table 4

j) On the grid provided plot a graph of Voltage, V (V) against Current, I (A)        (5marks)

k) Determine the slope of the of the graph                                                     (2marks)

l) Given that graph is related to equation  where E and r are the emf and internal resistance of the cells respectively, use your graph to determine the value of:

E =……………………                                                                                              (1mark)

r =……….………….                                                                                                 (1mark)