KNEC KCSE Physics Paper 3 Question Paper / 2016 Pre KCSE

Part A

You are provided with the following apparatus
 Concave mirror and a holder
 Meter rule
 Candle ( about 7cm)
 White screen
a) Determine the focal length of the mirror by focusing a distant object
f = ……………………………………………………………………………………(1mk)
b) Arrange the apparatus as shown in figure 1 below

c) Place the candle at a distance u =22cm from the mirror. Move the screen along the meter
rule until a sharp image is formed on the screen. Measure and record the image distance
V.
d) Repeat the experiments for other values of u and record your result in table 1 below..

e) Plot a graph of magnification , m(y-axis)against image distance v ( 5mks)
f) Given that m = v/f-1. Determine the focal length, f.(3mks)

Part B
You are provided with the following apparatus
 A voltmeter 0-3 or 0-5v
 An ammeter ( 0-1A)
 10Ω resister ( fixed)
 A switch
 One dry cell and a cell holder
 Six connecting wires
a) (i) Connect the above apparatus as shown in the circuit diagram below with the switch s
open.

ii) With the switch S open, record E the voltmeter reading (1 mk)
E =
……………………………………………………………………………………….
iii) Close the switch and record V, the voltmeter reading and I the ammeter reading
v = (1mk)
………………………………………………………………………………………..
I
=…………………………………………………………………………………………

iv) Given that E –V = Ir, Find r the fro the dry cell. ( 2mks)

Part A
You are provided with the folowng
 A triangular prism
 A piece of soft board
 Four ( 4) optical pins
 A sheet of plain paper
 Thumb pins
Proceed as follows:
a) Place the plain sheet of paper on the soft board . Trace the triangular outline of the prism
on the sheet of paper. Remove the prism and use a ruler to extend the three sides of the
outline

Use a protractor to measure the refracting angle R of the prism.
R =…………………………………………………………………………………………( 1mk)

b) On the side AB of the triangular prism outline,. Draw a normal at a point half-way
between A and B. ( This normal will be used for the rest of the experiment).
c) Draw a line at an angle i-30^o to the normal. Stick two pins P₁ and P₂ vertically on this
line. See figure 3 above.
d) Place the prism accurately on the outline. By viewing through the prism from side AC.
Stick two other pins P₃ and P₄ vertically such that they are in line with the images of pins
P₁ and P₂
Remove the prism and the pins. Draw a line joining marks made by P3 and P4 . Extending
this line to meet AC. See figure 4 below.
Measure and record in tale 2 below the value of angle o

e) Repeat the procedures in © and (d) above for other values of I shown in table 2.
Complete the table.
Table 2

F) On the grid provided plot the graph of the angle of the emergency E(yaxis) against the
Angle of incidence i
(5mks)
ii) Use the graph to find i(the angle of incidence at which i=E) ( 1mk)
( The teacher to collect the plane papers used for this experiment showing how the
øis got.).

PART B
You are provided with the following
 Meter rule
 Report stand, clamp and boss
 500ml beaker ¾ full of water
 100g mas
 50g mass
 Three pieces of thread
Proceed as follows
a) Balance the meter rule horizontally by suspending it from the stand and clap with one of
the threads . Record the balance point G.
G =…………………………………………………….(cm) ( 1mk)
b) 9i) Suspend the 100g mass from the meter rule at a point x such that x = 10cm from pont
G. With l00g mass completely immersed in water in the beaker, hang the 50 g mass from

the meter rule and adjust its position until the system is in equilibrium as shown in the
diagram below.

Note the point of suspensuion P of the mass ( 50g)
P =……………………………………………………………. ( 1mk)
ii) Find the value of Y.
Y……………………………………………………………………………………..(1mk)
(iii) Using the information above, calculate the up thrust on the 100g mass if the density of water
is 1000kg/m³. (3mks)