Circular Motion

Question 1

What is angular displacement

Answer 1

angle through which an object turns about the centre of a circle

Question 2

What is radian?

Answer 2

angle subtended at the centre of a circle by an arc equal in length to the radius of the circle

Question 3

What is angular velocity?

Answer 3

rate of change of angular displacement

Question 4

What is centripetal force?

Answer 4

a resultant force acting on a rotating object which moves in uniform circular motion, centripetal force always points towards centre of rotation

Question 5

What is uniform circular motion?

Answer 5

motion of an object moving in a circular path at constant speed

Question 6

Why is there a resultant force acting on a ball moving at constant speed in a circular path?

Answer 6

• although the speed is constant, the direction of the ball is always changing, hence its velocity is changing, thus the ball accelerates
• By Netwon’s second law, a resultant force must have acted on it

Question 7

Why does centripetal force point towards the centre of rotation?

Answer 7

• since the object moves with constant tangential speed, the tangential force is 0
• resultant force must act perpendicular to the path such that the force only changes direction but not tangential speed

Question 8

What is frequency?

Answer 8

an object in circular motion is the number of revolutions made by the object per unit time

Question 9

What is period?

Answer 9

the time taken for the object to make one complete revolution