Gas + Fire + Basketball + Newton = bad idea

First, don't play with fire. Fire is dangerous. You can get hurt. Here is a video of two guys trying to (presumably) make the Miami Heat flaming basketball.


Note: the above is just a picture link to the actual movie. Embedding the movie was doing some weird stuff. In the movie, two guys pour gasoline on a basketball and then light it on fire. One of the guys then gives the ball a good kick. The result is that some of the flaming gas stays in place and some goes with the ball (and some gets on the guy's foot).

This could be a good example of the momentum principle (also know as Newton's second law). This says:


This form of the momentum principle works if the force is constant or if the time is very short. So, for the gasoline on the ball, there is a small force for a short period of time (the guy kicked the ball, not the gasoline). The result is that the change in momentum of the gasoline is very small (essentially zero) and it stays in place. When you watch the video, at first it seems like the ball did not even leave because of the left over burning gasoline.

This is similar to the classic demo of pulling out a tablecloth from under some dishes. Here is my version of that.

Inertial demo from Rhett Allain on Vimeo

Really a fun demo that you can do at home (don't do the flaming basketball at home).

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