Centripetal Force
- Centripetal force can be calculated using any of the following equations:
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)
- The centripetal force is the resultant force on the object moving in a circle
- This is particular important if there are multiple forces on the object, such as weight
Worked Example
A bucket of mass 8.0 kg is filled with water is attached to a string of length 0.5 m.
What is the minimum speed the bucket must have at the top of the circle so no water spills out?
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