Physics – Cambridge AS Level: Work Energy and Power
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There are twenty questions in this quiz. Select the correct answer from the given choices.
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Question 1 of 20
1. Question
1 point(s)A block of weight W is pulled up a rough slope by a force F. When the block has moved a distance x along the slope, it has risen height h.
Which expressions give the amount of work done on the block and the amount of gravitational potential energy gained by the block?work done gravitational potential
energyA Fx Wh B Fh Wx C Wx Fh D Wh Fx CorrectIncorrectHint
Equations of work done and gravitational potential energy

Question 2 of 20
2. Question
1 point(s)A pendulum bob oscillates between P and R.
Assuming the gravitational potential energy lost in moving from P to Q is converted into kinetic energy, what is the speed of the bob at Q?CorrectIncorrectHint
mgh = 1/2 mv^2

Question 3 of 20
3. Question
1 point(s)Which operation involves the greatest mean power?
CorrectIncorrectHint
Power is same as force times velocity

Question 4 of 20
4. Question
1 point(s)The diagram shows two pulley wheels connected by a belt.
Wheel Q is driven by a motor and rotates clockwise at a constant rate. Wheel Q puts tension in the top portion of the belt, which in turn drives the wheel P. The lower portion of the belt is slack and has no tension. The weight of the belt and frictional forces are negligible.
The diameter of P is 150 mm. The diameter of Q is 100 mm. The torque applied to Q is 3.0 N m.
What is the tension in the belt and the torque on wheel P?tension in top of belt
/ Ntorque on wheel P
/ N mA 20 2.0 B 30 4.5 C 40 2.0 D 60 4.5 CorrectIncorrectHint
The tension in the belt between P and Q is the same.

Question 5 of 20
5. Question
1 point(s)A projectile is launched at 45° to the horizontal with initial kinetic energy E.
Assuming air resistance to be negligible, what will be the kinetic energy of the projectile when it reaches its highest point?CorrectIncorrectHint
At the highest point, the vertical component of velocity of the projectile is zero

Question 6 of 20
6. Question
1 point(s)Two trolleys are placed together on a horizontal runway with a compressed spring between them.
When they are released, the 2 kg trolley moves to the left at 2 m s^{–1}.
How much energy was stored in the spring?CorrectIncorrectHint
Sum of momentum before collision = Sum of momentum after collision

Question 7 of 20
7. Question
1 point(s)An electric railway locomotive has a maximum mechanical output power of 4.0 MW. Electrical power is delivered at 25 kV from overhead wires. The overall efficiency of the locomotive in converting electrical power to mechanical power is 80 %.
What is the current from the overhead wires when the locomotive is operating at its maximum power?CorrectIncorrectHint
Output power / Input power = 80 / 100

Question 8 of 20
8. Question
1 point(s)What is the internal energy of a system?
CorrectIncorrectHint
Knowledge based question

Question 9 of 20
9. Question
1 point(s)The diagram shows a lift system in which the elevator (mass m_{1}) is partly counterbalanced by a heavy weight (mass m_{2}).
At what rate does the motor provide energy to the system when the elevator is rising at a steady speed v ? (g = acceleration of free fall)CorrectIncorrectHint
The rate at which the motor provides energy is the power of the motor

Question 10 of 20
10. Question
1 point(s)A box of weight 200 N is pushed so that it moves at a steady speed along a ramp, through a height of 1.5 m. The ramp makes an angle of 30° with the ground. The frictional force on the box is 150 N while the box is moving.
What is the work done by the person?CorrectIncorrectHint
This component of the weight, along with the frictional force opposes the motion. But since the box moves at a steady speed,
the resultant force on the box is zero (there is no acceleration). This means that that the person is providing a force equal to
the sum of these 2 forces. 
Question 11 of 20
11. Question
1 point(s)A raindrop of mass m is falling vertically through the air with a steady speed v. The raindrop experiences a retarding force kv due to the air, where k is a constant. The acceleration of free fall is g.
Which expression gives the kinetic energy of the raindrop?CorrectIncorrectHint
acceleration is zero

Question 12 of 20
12. Question
1 point(s)What are units of work, energy and power?
work energy power A J N m J B J s^{–1} J J s^{–1} C N m N m W D N m W W CorrectIncorrectHint
J = Nm

Question 13 of 20
13. Question
1 point(s)In order that a train can stop safely, it will always pass a signal showing a yellow light before it reaches a signal showing a red light. Drivers apply the brake at the yellow light and this results in a uniform deceleration to stop exactly at the red light.
The distance between the red and yellow lights is x.
What must be the minimum distance between the lights if the train speed is increased by 20 %, without changing the deceleration of the trains?CorrectIncorrectHint
Since there is a uniform deceleration, we can use the equations of uniformly accelerated motion.

Question 14 of 20
14. Question
1 point(s)The diagram shows a particle X, with kinetic energy E_{k}, about to collide with a stationary particle Y. Both particles have the same mass.
After colliding, X and Y travel onwards together as a single larger particle.
How much kinetic energy is lost in the collision?CorrectIncorrectHint
In any closed system, momentum is always conserved.

Question 15 of 20
15. Question
1 point(s)An electric motor is required to produce 120 W of mechanical output power. The efficiency of the motor is 80 %.
Which row is correct?electrical power
input to motor / Wwaste heat output
from motor / WA 120 24 B 120 96 C 150 30 D 150 120 CorrectIncorrectHint
Efficiency = Useful mechanical output power / Electrical power input

Question 16 of 20
16. Question
1 point(s)When a horizontal force F is applied to a frictionless trolley over a distance s, the kinetic energy of the trolley changes from 4 J to 8 J.
If a force of 2F is applied to the trolley over a distance of 2s, what will the original kinetic energy of 4 J become?CorrectIncorrectHint
Work done by force F (= Fs) = 8 – 4 = 4J So, Fs = 4J

Question 17 of 20
17. Question
1 point(s)The kinetic energy of a vehicle of mass 1000 kg is 4.5 × 10^{5} J. It is braked with a total constant braking force of 6000 N.
What will be its stopping distance?CorrectIncorrectHint
Work done to stop vehicle = Kinetic energy

Question 18 of 20
18. Question
1 point(s)In many oldstyle filament lamps, as much as 92 J of energy is emitted as thermal energy for every 8 J of energy emitted as light.
What is the efficiency of the lamp, as the percentage of electrical energy converted to light energy?CorrectIncorrectHint
Efficiency = useful output energy / total output energy

Question 19 of 20
19. Question
1 point(s)What is the unit of power in SI base units?
CorrectIncorrectHint
Knowledge based question

Question 20 of 20
20. Question
1 point(s)A piston in a gas supply pump has an area of 600 cm^{2} and it moves a distance of 40 cm during one stroke. The pump moves the gas against a fixed pressure of 5000 Pa.
How much work is done by the piston during one stroke?CorrectIncorrectHint
Work done = p × ΔV