##### Physics Paper 3 Question Paper

### KCSE CLUSTER TESTS 20

#### Physics Paper 3

You are provided with the following apparatus

- Complete retort stand

- Wooden wedge (knife edge)

- Two pieces of thread about (40cm and 20cm long)

- Mass Q=150g (you may combine a 100g and 50g mass to give 150g)

- Metre rule - A single pulley

- A 10g mass

- Three 20g masses

- A 50g mass

Proceed as follows:-

a) Balance the metre rule on the knife edge and record the reading at this point. Balance point

P=…………………………………………………………cm

b) Using the metre rule, knife edge, a piece of thread and a 50g mass Set up an apparatus to determine the weight of the metre rule.

i) Draw a diagram of the set up.

ii) Determine the weight of the metre rule

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c) Arrange the apparatus as shown in figure 1 below

P is the balance point of the metre rule.

Hang the mass Q on the metre rule and adjust its position so that the metre rule is in equilibrium when M=20g

i) Measure the distance y between the balance point P and the point where the thread round the pulley is attached on the metre rule.

The thread over the pulley must always be kept perpendicular to the metre rule y=……………………………………………………….cm

ii) Measure the distance, X, between the point of suspension of the mass Q and P the balance point.

Repeat for masses (M) 30g, 40g, 50g, 60g and 70g and each time measure the distance X

d) Complete table 1 below

f) Calculate the slope S of the graph

f) Calculate the slope S of the graph

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15 marks

You are provided with the following

- Rectangular glass block

- Four optical pins - Soft board

- Set square - A ruler / half metre rule

- A pair of compasses

- Three plain white paper

- A plane mirror

- Cellotape (about 15cm long)

- A protractor

- 4 office pins.

PART A

a) Set up the apparatus as shown in figure 2 below

i) Draw a circle of radius 5cm on the sheet of the white plain paper as shown above.

Draw a line XOY the diameter of the circle.

ii) Now draw a normal line AOB to XOY.

Using the drawing pins, stick the plain white paper on a soft board. iii) Using a pair of compasses and a pencil, measure a length of 0.7cm on a ruler.

Transfer this length to the circumference of the circle and cut arcs AS_{6}, AS_{5}, AS_{4,} AS_{3},AS_{2}, and AS_{1} such that AS_{6}=S_{6}S_{5}=S_{5}S_{4}=S_{4}S_{3}=S_{3}S_{2}=S_{2}S_{1}=0.7cm

iv) Join S1 to O and place the glass block on the plain paper so that its longest boundary edge lies along XOY. Trace the boundary of the glass block.

v) Place object pins P_{1} and P_{2} on the line OS1 and use pins P_{3} and P_{4} to locate the images of P_{1} and P_{2 }when observed by the eye through the glass block.

iv) Remove the glass block an join the points P_{3} and P_{4 }to meet the glass block boundary at I.

Join I to O so that it cuts the circumference of the circle at C.

v) Now draw object perpendicular lines S_{1}L and a corresponding image perpendicular line CD to the normal line AOB from the circumference.

vi) Measure the perpendicular lines S1L and CD.

b) Repeat the experiment for S_{2},S_{3},S_{4},S_{5} and S_{6} and in each case obtain and record objects perpendicular length and corresponding image perpendicular length Table 2

c) On the grid provided, plot a graph of object perpendicular length (y-axis) against image perpendicular length

d) Determine the slope of the graph (3mks)

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Note: The plane paper used must be collected with the question paper

**PART B **

Proceed as follows

i) Using the cellotape provided fix the plane mirror to the glass block along the side as shown in figure 3 below. The reflecting surface to face the glass block.

ii) With the use of the office pins, secure firmly a white plain paper on the board and place the glass block together with attached mirror on it.

iii) Draw the outline of the glass block together with the mirror.

iv) Remove the block and the mirror and draw a normal at B somewhere a quarter- way the length of the outline you drew in (iii) above.

v) Draw two different rays AB incident at B. The incident rays should make angles of 100 and 300 with the normal ON at B.

vi) Replace the glass block together with the attached mirror so as to exactly fit on the outline in (iii).

vii) Place two object pins P1 and P2 along the 100 line. Locate the images of pins P_{1} and P_{2} as they appear by non- parallax (the images of the pins appear to be in a straight line when viewed through the glass block) Place pins P3 and P4 so that the images of pins P_{1} and P_{2} are not seen

viii) Remove the glass block together with the attached mirror from the outline and produce the lines joining P_{1} to P_{2} and P_{3} to P_{4 }so that they intersect at C. Measure and record the perpendicular distance X in table 3 below

ix) Repeat the above with the 30^{0} line

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25 marks