What you need:
A small ball, and a jar with a mouth larger than the ball
What to do:
1. Keep the ball on a flat surface, like the floor or a table
2. Invert the jar over it.
3. Try to pick up the ball with the jar. Can you?
4. Now, start to move the jar in a circle around the ball. Gradually, increase the speed.
What happens:
Gradually increase the speed You can’t lift the ball with a stationary jar But when the jar is moving in a circular motion the ball also starts to move along the rim until it gradually moves up into the jar if you continue the circular movement, you can lift the jar right off the table without dropping the bas This takes a little practice though.
Why?
When the circular motion of the jar is smooth, the ball also begins to move in a circle inside the jar. This happens due to a force called centripetal force Centripetal force is the force that acts on a body that’s moving in a curved path while the speed of the ball (and the jars shape) makes it move in a circle, its centripetal force that keeps going. You can lift up the jar when the centripetal force on the ball becomes more than the gravitational force acting on it. Once you slow down or stop rotating the jar, the centripetal force decreases and gravity takes over once more, causing the ball to drop out.
Picture Credit : Google
