Download O- Levels : PHYSICS 1 (a) (i) Define power

O- Levels : PHYSICS
1 (a) (i) Define power.
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(ii) Use your definition in (i) to show that power may also be expressed as the product of force
and velocity.
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(b) A lorry moves up a road that is inclined at 9.0° to the horizontal, as shown in Fig. 1.1.
Fig. 1.1
The lorry has mass 2500 kg and is travelling at a constant speed of 8.5 m s−1. The force due toair
resistance is negligible.
(i) Calculate the useful power from the engine to move the lorry up the road.
Power = ............................................. kW [3]
(ii) State two reasons why the rate of change of potential energy of the lorry is equal to the
power calculated in (i).
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2 A uniform plank AB of length 5.0 m and weight 200 N is placed across a stream, as shown in
Fig. 2.1.
Fig. 2.1
A man of weight 880 N stands a distance x from end A. The ground exerts a vertical force FA on
the plank at end A and a vertical force FB on the plank at end B.
As the man moves along the plank, the plank is always in equilibrium.
(i) Explain why the sum of the forces FA and FB is constant no matter where the man stands on
the plank.
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(ii) The man stands a distance x = 0.50 m from end A. Use the principle of moments to calculate
the magnitude of FB.
FB = ...................................................... N [4]
3 Fig. 3.1 represents waves on the surface of water in a ripple tank at one particular instant of
time.
Fig. 3.1 (not to scale)
A vibrator moves the surface of the water to produce the waves of frequency f. The speed of the
waves is 7.5 cm s−1. Where the waves travel on the water surface, the maximum depth of the
water is 15 mm and the minimum depth is 12 mm.
(i) Calculate, for the waves,
1. The amplitude,
Amplitude =.................................................. mm [1]
2. The wavelength.
Wavelength =..................................................... m [2]
(ii) Calculate the time period of the oscillations of the vibrator.
time period = ...................................................... s [2]
(c) State and explain whether the waves on the surface of the water shown in Fig. 3.1 are
transverse or longitudinal.
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4 (a) Explain what is meant by a scalar quantity and by a vector quantity.
scalar:
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vector:
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(b) A ball leaves point P at the top of a cliff with a horizontal velocity of
15 m s–1, as shown in Fig. 4.1.
Fig. 4.1
The height of the cliff is 25 m. The ball hits the ground at point Q.
Air resistance is negligible.
(i) Calculate the vertical velocity of the ball just before it makes impact with the ground at Q.
vertical velocity = ................................................. m s–1 [2]
(ii) Show that the time taken for the ball to fall to the ground is 2.3 s.
[1] (iii) Calculate
the magnitude of the displacement of the ball at point Q from point P.
displacement = ...................................................... m [4]
(iv) Explain why the distance travelled by the ball is different from the magnitude of the
displacement of the ball.
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5 A student uses a voltmeter.
(a) State the quantity measured with a voltmeter.
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(b) Fig. 5.1 shows an analogue voltmeter.
Fig. 5.1
State the reading on the voltmeter.
reading = ...........................................................[1]
(c) A school has both digital and analogue voltmeters.
Suggest one advantage of using a digital voltmeter rather than an analogue voltmeter.
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(d) The student is asked to connect three 2.0 V cells in series with a resistor R of resistance 100
Ω. The student sets up the circuit as shown in Fig. 5.2.
Fig.5.2
(i) State the reading on the voltmeter when it is connected across
1. AD, reading =........................................................... [1]
2. AB, reading =........................................................... [1]
3. DC. reading = ...........................................................[1]
(ii) R is replaced by a resistor of resistance 1000 Ω. There is no change in the reading on the
voltmeter across DC. Explain this.
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6 A climber is supported by a rope on a vertical wall, as shown in Fig. 6.1.
Fig. 6.1
The weight W of the climber is 520 N. The rope, of negligible weight, is attached to the climber
and to a fixed point P where it makes an angle of 18° to the vertical. The reaction force R acts at
right angles to the wall.
The climber is in equilibrium.
(a) Complete Fig. 6.2 by drawing a labelled vector triangle to represent the forces acting on the
climber.
Fig. 6.2
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(b) Resolve forces or use your vector triangle to calculate
(i) the tension T in the rope,
T =...................................................... N [2]
(ii) the reaction force R.
R =...................................................... N [1]
(c) The climber moves up the wall and the angle the rope makes with the vertical increases.
Explain why the magnitude of the tension in the rope increases.
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