- A plastic bucket
- Head outside…just in case you get wet!
- Add water to the bucket, but don’t fill it to the top. You should be able to easily lift the bucket.
- Swing the bucket in a circle above your head.
What happens to the water?
Why did the water stay in the bucket? Did the water defy gravity???
No, gravity is still pulling the water down, but two other forces are also acting on the water: intertia and centripetal force.
- Inertia: Moving objects continue to move in a straight line, unless changed by an outside force.
- Centripetal force: The force that is necessary to keep an object moving in a curved path.
Because the water’s interia, it wants to continue to move in a straight line, and your arm is creating centripetal force in order to swing the bucket in a circle. This also causes the water to push against the bottom of the bucket.
Did you try swinging the bucket slowly? Did you get wet? If you got wet, its because the force of gravity was stronger than the centripedal force. This is a great experiment to try on a hot summer day!