Quick answer: Circular motion at constant speed involves a constant angular velocity ω = 2π/T and a centripetal acceleration a = v²/r = ω²r directed towards the centre. This Physics 11-12 test on circular motion has 8 questions worth 20 marks, to do in 45 minutes: centripetal acceleration, rotating disc and work done. The mark scheme is on a separate page; free printable PDF.
This test lasts 45 minutes and is worth 20 marks. You may also use a calculator. Take g = 9.81 N/kg, draw force diagrams where helpful, and then give final answers with units and sensible significant figures.
Level: Physics grades 11-12 (A Level · IB · Class 11-12) · Curriculum: A Level 3.6
Question 1 Centripetal acceleration (2 marks)
Firstly, state the direction of the acceleration of an object moving at constant speed in a circle. Then explain why it accelerates although its speed is constant.Question 2 Rotating disc (3 marks)
A disc of radius 6.0 cm turns at 480 rpm.- Firstly, calculate its angular velocity. (1 mark)
- Then calculate the speed of a point on the rim. (1 mark)
- Finally, calculate the centripetal acceleration of that point. (1 mark)
Question 3 Work done (2 marks)
Explain why the centripetal force on a satellite in a circular orbit does no work, so the speed stays constant.Question 4 Car on a flat bend (3 marks)
A car of mass 900 kg turns a flat bend of radius 50 m, and the coefficient of friction is 0.60.- Firstly, calculate the greatest speed at which it can turn without skidding. (2 marks)
- Then state whether a car of mass 1800 kg has a greater, equal or smaller limit. (1 mark)
Question 5 Ball in a vertical circle (3 marks)
A ball of mass 0.40 kg moves in a vertical circle of radius 0.90 m on a string.- Firstly, calculate the tension at the bottom when the speed is 6.0 m/s. (2 marks)
- Then calculate the minimum speed at the top. (1 mark)
Question 6 Banked road (3 marks)
A road bend of radius 150 m has a bank of 8.0° to the horizontal.- Firstly, state which force provides the centripetal force at the design speed. (1 mark)
- Then calculate the design speed at which no sideways friction is needed. (2 marks)
Question 7 Mud from a tyre (2 marks)
Mud flies off a spinning tyre in a straight line, but a student says a centrifugal force throws it outward. Therefore, explain what really happens.Question 8 Scaling (2 marks)
A car rounds a bend at speed v. Without calculating, state by what factor the friction needed changes if:- you double the speed on the same bend; (1 mark)
- you halve the radius at the same speed. (1 mark)
