5.2 Circular motion

Question 1

How do you convert degrees to radians?

Answer 1

To convert an angle from degrees to radians, divide it by 360 and then multiply by 2π.

Question 2

What is meant by the period of an object in circular motion?

Answer 2

The time taken for one full rotation.

Question 3

What is meant by the frequency of an object in circular motion?

Answer 3

The number of revolutions the object makes every second

Question 4

What is the symbol ω used to represent?

Answer 4

Angular velocity.

Question 5

What are the units of angular velocity?

Answer 5

rad s⁻¹

Question 6

Define angular velocity.

Answer 6

The angle travelled through per unit time.

Question 7

Define an object’s centripetal force.

Answer 7

A constant net force perpendicular to the velocity of an object which causes it to travel in a circular path.

Question 8

A satellite is moving at a constant speed in a circular orbit around the Earth. The only force acting on the satellite is its weight. Why does the satellite’s speed remain constant despite the unbalanced force acting on it?

Answer 8

The weight force acts perpendicular to the satellite’s velocity or motion. There is no component of the force in the direction of the velocity. Therefore, no work is done, and so there is no acceleration in the direction of motion.

Question 9

Explain how an object moving in a circle can be constantly accelerating without changing speed or kinetic energy. Use the term work done in your answer.

Answer 9

• The force causing circular motion (centripetal force) acts perpendicularly to the object’s velocity.
• Acceleration occurs because the force changes the direction of velocity, not its magnitude.
• No work is done because the force has no component in the direction of the motion.
• Without work done, the object’s kinetic energy and speed remain constant, even as it accelerates.