Force, energy and momentumAQA A-Level Physics: Topic test

20 questions, 54 marks

AQA A-Level Physics

Force, energy and momentum topic test

Total 54 marks

Name

Class

Date

1
Two tugs pull on a barge with horizontal forces that are at right angles to each other. Tug A pulls with a force of 4.0 kN due north and tug B pulls with a force of 3.0 kN due east.
(a)
What is the magnitude of the resultant of the two forces?
[1 mark]
A5.0 kN
B7.0 kN
C1.0 kN
D3.5 kN
(b)
What is the direction of the resultant, measured east of north?
[1 mark]
A53.1°
B25.4°
C36.9°
D45.0°
(c)
A third tug, C, also pulls on the barge so that the barge moves at constant velocity. State the magnitude and direction of the force that tug C exerts.
[2 marks]
Total for question 1: 4 marks
2
A wheelbarrow carries a load of weight 450 N. The line of action of the load is 0.50 m horizontally from the axle of the wheel. The person lifts the handles with a vertical force F at a horizontal distance of 1.40 m from the axle. The weight of the wheelbarrow itself can be ignored.
(a)
What is the moment of the load about the axle?
[1 mark]
A900 N m
B630 N m
C225 N
D225 N m
(b)
What is the force F that the person must exert on the handles to hold the wheelbarrow in equilibrium?
[1 mark]
A289 N
B161 N
C630 N
D225 N
(c)
Use the principle of moments to explain why the force needed to lift the handles gets smaller if the load is moved closer to the wheel.
[2 marks]
Total for question 2: 4 marks
3
A car of mass 1100 kg is travelling at 20 m s⁻¹ along a straight, level road. The driver brakes and the car stops under a constant braking force of 5500 N. The driver has a reaction time of 0.70 s, during which the car continues at 20 m s⁻¹.
(a)
Calculate the deceleration of the car and the distance it travels while braking.
[3 marks]
(b)
Calculate the total stopping distance, including the reaction time. State and explain how the braking distance changes if the road is wet.
[4 marks]
Total for question 3: 7 marks
4
A ballistic pendulum is used to measure the speed of a bullet. A bullet of mass 20 g is fired horizontally at 400 m s⁻¹ into a stationary wooden block of mass 3.98 kg that hangs from long, light strings. The bullet embeds in the block, coming to rest relative to the block in 0.50 ms, and the block and bullet then swing upwards together. Take g = 9.81 m s⁻².
(a)
Show that the speed of the block immediately after the bullet embeds is 2.0 m s⁻¹. Calculate the maximum height through which the block and bullet rise.
[6 marks]
(b)
Show that the collision is inelastic. Explain what happens to the lost energy. Calculate the average force exerted on the bullet while it comes to rest relative to the block.
[6 marks]
Total for question 4: 12 marks
5
A tennis player serves, hitting the ball horizontally at 28 m s⁻¹ from a point 2.45 m above level ground. Ignore air resistance and take g = 9.81 m s⁻².
(a)
How long does the ball take to reach the ground?
[1 mark]
A0.50 s
B0.71 s
C0.088 s
D0.25 s
(b)
What is the horizontal distance travelled by the ball before it hits the ground?
[1 mark]
A14.0 m
B39.6 m
C2.45 m
D19.8 m
(c)
Calculate the speed of the ball as it hits the ground.
[2 marks]
Total for question 5: 4 marks
6
A steel ball of mass 0.040 kg is released from rest at the surface of a tall cylinder of oil. It accelerates downwards, but its speed eventually becomes constant. Ignore upthrust. Take g = 9.81 m s⁻².
(a)
Which statement is correct when the ball is moving at its terminal speed?
[1 mark]
AThe ball has a constant acceleration of 9.81 m s⁻².
BThe resultant force on the ball is upwards.
CThe drag on the ball is equal in magnitude to its weight.
DThe drag on the ball is zero.
(b)
At one instant the drag on the ball is 0.15 N. What is the acceleration of the ball at this instant?
[1 mark]
A6.1 m s⁻²
B3.8 m s⁻²
C9.8 m s⁻²
D13.6 m s⁻²
(c)
A second steel ball of the same size but of greater mass is released in the same oil. State and explain how its terminal speed compares with that of the first ball.
[2 marks]
Total for question 6: 4 marks
7
A crane motor with an input power of 3.6 kW lifts a load of mass 600 kg vertically through 12 m at a constant speed of 0.50 m s⁻¹. Take g = 9.81 m s⁻².
(a)
Calculate the useful work done on the load and the useful output power of the crane.
[3 marks]
(b)
Calculate the efficiency of the crane. Calculate the energy wasted during the lift and state what happens to it.
[4 marks]
Total for question 7: 7 marks
8
A fielder throws a cricket ball of mass 0.16 kg vertically upwards from hand height at 18 m s⁻¹. Air resistance is negligible. The ball is caught by a wicketkeeper at the same height as it was thrown, and is brought to rest by the hands in 0.030 s. Take g = 9.81 m s⁻².
(a)
Calculate the maximum height reached by the ball using an equation of motion. Show that conservation of energy gives the same height, and calculate the total time between the throw and the ball reaching the wicketkeeper.
[6 marks]
(b)
Calculate the average resultant force on the ball while it is being caught. Explain why the wicketkeeper moves the hands backwards while catching the ball, and calculate the average force if this doubles the stopping time.
[6 marks]
Total for question 8: 12 marks

End of questions

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).