1. Calculate the circumference of a circle with a radius of 0.2 m.

2. If a vibrating mobile phone vibrates 540 times in one minute, calculate the frequency of vibration. Also calculate the period of vibration.

3. Describe the difference between “Speed” and “Velocity”

4. What does ‘RPM’ stand for?

Circular Motion

Definition: Motion of an object moving in a circular path

Examples:

As Scott swings the hammer it takes 0.6 seconds to go around once. The combined radius of Scott’s arms and the chain is 1.2 m.

Calculate the speed of the hammer.

Centripetal Acceleration

Centripetal Force

There is a car moving in a circular path (e.g. a roundabout) with the radius of 5 m. It takes 12 seconds for the car to go around once.

a) Calculate the speed of the car.

b) Calculate the centripetal acceleration of the car.

c) Calculate the centripetal force acting on the car.

Question!

What would happen if the centripetal force is suddenly removed?

Scott swings a 7kg hammer. Calculate the centripetal acceleration AND the centripetal force if:a) Radius = 1.2 m, Speed = 6 ms-1

b) Radius = 1.2 m, Speed = 12 ms-1

c) Radius = 0.6 m, Speed = 6 ms-1

d) Radius = 1.2 m, Period = 0.7 sec

The battles between Fc, v and r

What would happen to Fc if:a) The speed is increased?b) The radius is increased?c) The period is increased?d) The frequency is increased?

Homework: Homework Booklet Worksheet SEVEN

Mechanics Exam Paper Circular Motion

Activity 12A (page 143)