Motion of a Ping-Pong

Have you ever use your finger to press down one side of the ping-pong ball?

However, a few seconds later, the ping-pong starts to rolling back toward you. Why?

The ball starts with an initial velocity Vo, and an initial angular velocity wo.

When the velocity of the contact point related to the table V - r w

Is it passible to let the ball stop? (velocity V=0.) or moving forward(V>0.)?

Under what kinds of conditions? This java applet let you play with it. Enjoy!

The initial velocity of the ball is fixed. Vo= 20 cm/s. The radius of the ball r = 10. cm;

You can change different initial angular velocity wo ( r*wo was shown).

Press start button to starts the java animation.

The white arrow below the ball represent the friction force.

Press Clear to clear the curves (Velocity V verses time t).

You can also change the friction coefficient u.

How to calculate?

Your suggestions are highly appreciated! Please click

Author:Fu-Kwun Hwang, Dept. of physics, National Taiwan Normal University
Last modified :