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Name: . ………………………………………..…………….. Index No.:………………………

School:……..………………………………………………… Adm. No ……………………….

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PHYSICS

Paper 1

Time: 2 hours

PHYSICS PREDICTION - 2017 Kenya Certificate of Secondary Education (K.C.S.E)

INSTRUCTIONS TO CANDIDATES

Write your name and index number in the spaces provided .

This paper consists of Two sections: A and B.

Answer all the questions in section A and B in the spaces provided.

ALL working MUST be clearly shown.

Mathematical tables and electronic calculators may be used.

FOR EXAMINER’S USE ONLY

Section Question Maximum score Candidate’s score

A 1 – 11 25

B 12

13

14

15

16

10

12

12

12

9

80

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SECTION A (25 Marks)

Answer all the questions in the spaces provided.

1. A micrometer screw gauge is used to measure the diameter of a copper wire. The reading with the wire in position is shown in diagram 1. The wire is removed and the jaws of the micrometer are closed. The new reading is shown in diagram 2.

What is the diameter of the wire?

[3m]

2. The diagram shows a sealed container filled with air and attached to a manometer. The liquid in the manometer has a density of 1200 kg m−3. Atmospheric pressure is 1.02 x 105 Pa.

Calculate the pressure of the air inside the sealed container.[3M]

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3. On the axis below, sketch the variation of density of water with temperature if it is heated from 00C to 100C.[1m]

Mark the point at which the volume of a given mass of this water sample is mimimum?

[1m]

Total [2m]

4. When we blow air over a strip of paper as shown in the above figure, we find that the paper moves upwards.

Explain this observation

[Total 2m]

4

5. A man of weight 600 N stands at the end of a uniform wooden plank, which is pivoted as shown in the diagram.

What is the weight of the wooden plank?

[2]

6. The velocity–time graph is for a stone thrown vertically upwards.

When time t = 3 s, what is the displacement of the stone from its starting position?

[2]

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7. The diagram shows an 80 kg person in a lift.

The normal contact force acting on the person from the base of the lift is R. Determine the

magnitude of R when the lift is accelerated upwards at 2.3 m s−2.

[3]

8. The graph above shows the force acting on a trolley of 5 kg mass over a distance of 10 m. Find the work done by the force to move the trolley.

[2m]

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9. A piece of aluminium of volume 200 cm3 and density 2.7 gcm-3 is completely immersed in kerosene. Determine; (i) Upthrust exerted on the piece of aluminium

[2m] (ii) How much will it weigh in kerosene? (Density of kerosene = 0.8 g cm-3)

[1m] [Total 3m]

10. State the major difference between a dry cell and a wet cell.

(1mk)

11. A length was measured using a meter-rule as shown.

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(a) Use the figures to indicate the correct position in which the reading should be taken. ………………………………………………………………………………………………………………………………… [1m] (b) Why must the eye be positioned in the place you have chosen? ………………………………………………………………………………………………………………………………….[1m]

[Total 2m]

SECTION B (55 Marks)

Answer all the questions in the spaces provided.

12. A spring is placed on a flat surface and different weights are placed on it, as shown in Fig. 2.1.

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The variation with weight of the compression of the spring is shown in Fig. 2.2.

The elastic limit of the spring has not been exceeded. (a) (i) Determine the spring constant k of the spring.

k =........................................... N m-1 [2] (ii) Deduce that the strain energy stored in the spring is 0.49 J for a compression of 3.5 cm.

[2]

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(b) Two trolleys, of masses 800 g and 2400 g, are free to move on a horizontal table. The spring in (a) is placed between the trolleys and the trolleys are tied together using thread so that the compression of the spring is 3.5 cm, as shown in Fig. 2.3.

Initially, the trolleys are not moving. The thread is then cut and the trolleys move apart. (i) Deduce that the ratio:

[2] (ii) Use the answers in (a)(ii) and (b)(i) to calculate the speed of the trolley of mass 800 g. Speed = ........................................... m s-1 [4]

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13. A skydiver jumps from an aircraft. (a) (i) The figure below, draw arrows to show the two main forces acting on her. Label the arrows with the names of the forces.

(ii) Which of the forces you have labelled will be the larger just after she jumps? Explain your answer.

[1] (b) (i) On the figure below, draw arrows to show the two main forces acting on her when the parachute has opened. Label the arrows with the names of the forces.

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(ii) How do the forces in Fig. 2 compare with the forces in Fig. 1? Explain your answer.

[2]

(c) The speed-time graph in Fig. 3 shows her descent.

(i) Which section of the graph shows the skydiver travelling with an acceleration which is not uniform?

Explain your answer.

[2]

(ii) At which point does she open her parachute? Explain your answer.

[2]

(iii) How long after opening her parachute does she reach the ground? Explain your answer.

[2]

[Total 12m]

12

14. The figure shows the horizontal forces acting on a moving car.

(a) Compare the sizes and directions of the two forces when the car is (i) moving along a straight road at constant speed, ………………………………………………………………………………………………………………………………………[1] (ii) accelerating. ………………………………………………………………………………………………………………………………………[1] (b) Suggest the direction of the resultant force on the car when the car turns a corner at constant speed. ……………………………………………………………………………………………………………………………………….[1] (c) Fig. 9.2 shows the speed-time graph for the first 24 s of the motion of the car along a straight road.

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(i) During the motion there is a period of uniform acceleration. State both the start and finish times of this period. ………………………………………………………………………………………………………………………………………[1] (ii) State the main energy changes that occur in the 24 s. ........................................................................................... ........................................................................................... ...........................................................................................

[3] (iii) Calculate the acceleration of the car during the first 5 s. State clearly the equation that you use.

[3] (iv) Determine the distance travelled in the first 5 s.

[3] (d) The car is stopped by applying the brakes. Various factors can affect the distance travelled by the car during the time that the brakes are applied. Apart from the force applied by the brakes,state two of these factors. ………………………………………………………………………………………………………………………………………[2]

[Total 12m] 15. A ball has mass m. It is dropped onto a horizontal plate as shown in Fig. 4.1.

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Just as the ball makes contact with the plate, it has velocity v, momentum p and kinetic energy Ek. (a) (i) Write down an expression for momentum p in terms of m and v. ...........................................................................................

(ii) Hence show that the kinetic energy is given by the expression

[3]

(b) Just before impact with the plate, the ball of mass 35 g has speed 4.5ms-1. It bounces from the plate so that its speed immediately after losing contact with the plate is 3.5ms-1. The ball is in contact with the plate for 0.14 s. Calculate, for the time that the ball is in contact with the plate, (i) the average force, in addition to the weight of the ball, that the plate exerts on the ball,

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Magnitude of force = .................................... N

Direction of force = ........................................ [4]

(ii) The loss in kinetic energy of the ball.

Loss = ....................................... J [2] (c) State and explain whether linear momentum is conserved during the bounce.

[3]

16. A stone on a string is whirled in a vertical circle of radius 80 cm at a constant angular speed of 16 radians per second.

Calculate the speed of the stone along its circular path.

...........................................................................................

...........................................................................................

...........................................................................................

Speed = ......................................................... (2)

Calculate its centripetal acceleration when the string is horizontal.

...........................................................................................

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...........................................................................................

...........................................................................................

Acceleration = ......................................................... (2)

Calculate the resultant acceleration of the stone at the same point.

...........................................................................................

...........................................................................................

...........................................................................................

Resultant acceleration = ......................................................... (3)

Explain why the string is most likely to break when the stone is nearest the ground.

...........................................................................................

...........................................................................................

...........................................................................................

........................................................................................... (2)

(Total 9 marks)