Paper 2 Circular Motion Drills

Q1 Rotating platform

A small marker on a rotating platform is $0.320\mathrm{m}$ from the centre. The platform rotates at $45.0$ revolutions per minute.

1. Convert the angular speed to $\mathrm{rad}{\mathrm{s}}^{-1}$. [2]
2. Calculate the tangential speed of the marker. [2]
3. Calculate the centripetal acceleration of the marker. [2]
4. State the direction of the acceleration. [1]

Q2 Horizontal circular motion

A $0.150\mathrm{kg}$ rubber stopper moves in a horizontal circle of radius $0.750\mathrm{m}$ at speed $4.20\mathrm{m}{\mathrm{s}}^{-1}$. The string is approximately horizontal.

1. Calculate the centripetal acceleration. [2]
2. Calculate the tension in the string. [2]
3. Explain why “centripetal force” should not be added as another force on the free-body diagram. [2]

Q3 Circular-motion reasoning

A car travels round a flat circular bend at constant speed.

1. Identify the real force that provides the horizontal inward resultant. [1]
2. Explain why the car can have acceleration even though its speed is constant. [2]
3. State and explain what happens to the required inward force if the car enters the same bend at a larger speed. [2]