Circular motion

Question 1

When will a body move in a circular path and will it be changing velocity?

Answer 1

when its motion is at right angles to a force that acts inwards along the radius of the path
the velocity will be changing

Question 2

What type of quantity is velocity and when does it change?

Answer 2

vector

when either its speed or direction of motion changes

Question 3

What is the name for the force that acts inwards along the radius of a circle?

Answer 3

centripetal force

Question 4

Give an example of centripetal force

Answer 4

• a satellite in orbit around the Earth
• gravity acts at 90° to the satellite
• it is accelerating even if the speed stays constant
• if there were no forces acting on it it would move in a straight line
• a motorbike moving around a bend
• the friction between the tyres and the road provides the centripetal force

Question 5

Name the 4 main types of centripetal force and give an example of them

Answer 5

gravitational: orbiting satellite
frictional: car on a roundabout
tension: a hammer thrower
electrostatic: electron orbiting nucleus

Question 6

A motorcyclist is travelling around a circular curve in a flat road. What is providing the centripetal force?

A: gravity
B: the friction between the tyres and the road
C: the normal reaction of the road on the tyres
D: the thrust of the engine

Answer 6

B

the centripetal force acts at right angles to the direction of motion and towards the centre of the circle