• An object moving in a circle is not in equilibrium, it has a resultant force acting upon it
  • This is known as the?centripetal force?and is what keeps the object moving in a circle
• The centripetal force (F) is defined as:

The resultant force towards the centre of the circle required to keep a body in uniform circular motion. It is always directed towards the centre of the body's rotation.

• ?Centripetal force can be calculated using:

Centripetal force is always perpendicular to the direction of travel

• Where:
  • F?= centripetal force (N)
  • v?= linear velocity (m s^-1)
  • ? = angular speed (rad s^-1)
  • r?= radius of the orbit (m)

• Note:?centripetal force and centripetal acceleration act in the?same direction
  • This is due to?Newton’s Second Law
• The centripetal force is?not?a separate force of its own
  • It can be any type of force, depending on the situation, which keeps an object moving in a circular path

Examples of centripetal force

Step 1: Draw the forces on the bucket at the top

Step 2: Calculate the centripetal force

• • The weight of the bucket = mg
  • This is equal to the centripetal force since it is directed towards the centre of the circle

Step 3: Rearrange for velocity?v

• • m?cancels from both sides

Step 4: Substitute in values