Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: colmack2 on 15/11/2017 23:21:29

Title: Why does my swiss ball roll away after I get off it?
Post by: colmack2 on 15/11/2017 23:21:29

Trivial but puzzling: After exercising on my Swiss Ball (on carpet), I stand up and after a few seconds the ball starts to roll. The floor is level. Any hypotheses?

Title: Re: Why does my swiss ball roll away after I get off it?
Post by: chris on 15/11/2017 23:22:03

Can you post a video?

Title: Re: Why does my swiss ball roll away after I get off it?
Post by: Kryptid on 16/11/2017 03:19:28

The ball is made of rubber, right? Maybe static electricity has something to do with it. Does it always move in the same direction?

Title: Re: Why does my swiss ball roll away after I get off it?
Post by: RD on 16/11/2017 04:40:55

Quote from: colmack2 on 15/11/2017 23:21:29

...After exercising on my Swiss Ball (on carpet), I stand up and after a few seconds the ball starts to roll. The floor is level. Any hypotheses?

The weight of the air-valve will give it a bias ...

(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=71863.0;attach=24312;image)

Title: Re: Why does my swiss ball roll away after I get off it?
Post by: chris on 16/11/2017 07:24:45

Quote from: RD on 16/11/2017 04:40:55

Quote from: colmack2 on 15/11/2017 23:21:29

...After exercising on my Swiss Ball (on carpet), I stand up and after a few seconds the ball starts to roll. The floor is level. Any hypotheses?

The weight of the air-valve will give it a bias ...

(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=71863.0;attach=24312;image)

The simplest explanations are always the best, and usually right! Thanks @RD for pointing out the obvious!

Title: Re: Why does my swiss ball roll away after I get off it?
Post by: evan_au on 16/11/2017 10:42:09

When you stand up, the back of your knees give the ball a slight backwards push?