CE PHYSICS - PAPER I
Name : ______Time allowed : hours
Class : ______Total no. of papers : 9
Class no. : ______Full marks : 90 marks
INSTRUCTIONS FOR PAPER
1.This paper consists of six questions each carrying 15 marks.
2.Answer ALL questions in this paper.
3.Take g = 10 ms-2 if necessary.
4.Some questions contain parts marked with an asterisk (*). In each of these parts, one mark is allocated to assess students’ ability in effective communication.
5.Some useful formulae in CE Physics are listed below :
(a) Relationship between initial velocity u, uniform acceleration a, final velocity v and displacement travelled s after time t :
(1) (2)
(3)
(b) Equivalent resistance of two resistors R1 and R2 :
(1)in series :
(2)in parallel :
(c)
Take g = 10 ms-2
QUESTION 1
Figure (a) shows a block X of mass 0.5 kg sliding down a plane inclined at an angle 30 oC with the horizontal. The plane is composed of two portions made of different materials. They join at B. The speed-time graph of the block is shown in Figure (b). PQ denotes the motion of the block in portion AB while QR denotes the motion in portion BC.
(a)Draw a diagram to show all the forces acting on the block. Label the forces. (3 marks)
(b)Describe briefly a method to check whether the speed of the block in the portion AB remains constant (2 marks)
(c)Find
(i)the net force,and
(ii)the frictional force
acting on the block X in the portion AB of the inclined plane.
(3 marks)
(d)Find
(i)the acceleration of,and
(ii)the distance travelled by
the block X in the portion BC of the inclined plane. (4 marks)
(e)If the block X is projected upwards from point C along the inclined plane with a certain initial speed, sketch the speed-time graph of the upward motion. (Assume that the block passes through point B of the plane.) (3 marks)
QUESTION 2
As shown in the figure, a screw jack is used to lift a load of 4000 N by applying a force of 10 N to the handle. The pitch of the screw is 1.5 X 10-3 m and the length of the handle is 0.2 m.
(a)What is the work done by a man in turning the handle through five revolutions ? (Where necessary, take = 3). (2 marks)
(b)Calculate the corresponding gain in potential energy of the load.
(2 marks)
(c)Find the efficiency of this machine ? (2 marks)
(d)Give TWO reasons why the screw jack is not 100 % efficiency.
(2 marks)
(e) (i)It is found that when the load is raised and the handle is let go, the screw jack does not turn backwards. Explain briefly.
(ii)Would the same observation apply to the screw jack if it was 100 % efficient ?
(2 marks)
(f)If the load is raised with a velocity of 3 X 10-3 ms-1, what must be the power developed by the man turning the handle ? (3 marks)
(g)Sketch a graph to show how the efficiency of a machine varies as the load is increased. (2 marks)
QUESTION 3
In figure above, the loudspeakers S1 and S2, are fed from a signal generator of wavelength 200 cm, so that they emit sound waves in phase. The speed of sound waves in air is 340 ms-1.
(a)What is the frequency of the sound wave. (1 mark)
(b)If the lengths of S1M and S2M are 5 m and 4 m respectively, what kind of interference occurs at M ? Explain briefly. (1 mark)
(c)When the receiver is moved along MQ, the signal received is first found to be maximum at N. What is the path difference between S1N and S2N ? (2 marks)
(d)On the same axes sketch two graphs of variation of the signal display on the C.R.O. at M, one for the signal from S1, the other for the signal from S2. Meanwhile, on the same axes sketch a third graph showing the signal at M due to signals from both S1 and S2. (3 marks)
(e)In exactly the same way, sketch three graphs of variation of the signal display on the C.R.O. at N. (3 marks)
(f)On the same axes sketch two graphs of variation of the signal display on the C.R.O. due to both S1 and S2 at C and B. (2 marks)
(g)If one of loudspeaker is suddenly out of order, a student suggests that the loudness recorded along PQ should be as shown below. Is he correct ? Explain briefly with the aid of a correct graph. (3 marks)
QUESTION 4
(a)The circuit diagram below shows a simple a.c. power supply unit suitable for providing 12 V, 50 Hz a.c. voltage for a lamp from a 240 V, 50 Hz a.c. mains supply. (Assume the transformer is ideal.)
(i)What is the purpose of the earth wire ? What other part of the a.c. power supply unit should be connected to the earth wire ? (2 marks)
(ii)What is the purpose of the fuse ? (1 mark)
(iii)Why the switch should be connected to the live wire instead of to the neutral wire. (2 marks)
(iv)Find the maximum number of lamps (12 V, 24 W) that can be connected in parallel to the a.c. power supply without blowing the 15 A fuse. (2 marks)
(v)Give a reason why the lamps are all connected in parallel instead of in series. (1 marks)
(vi)Calculate the total cost of electricity consumed in running the lamps mentioned in (iv) for 5 hours. The cost of electricity is 70 ¢ per kWh. (2 marks)
(b) (i)What circuit component is needed to place in the region P so that a d.c. voltage can be provided by the power supply ? (1 mark)
(ii)When an oscilloscope is connected across the points marked A and B on the circuit diagram above, the screen appears as shown below :
Sketch diagrams to show the screen when the oscilloscope is connected first across points C and D and then across points E and F of the circuit. (2 marks)
(iii)With the lamp connected to this d.c. power supply, it is found that the lamp is dimmer than it should be. Explain briefly.
(2 marks)
QUESTION 5
Figure (a)
1