# Homework Help: The Physics Behind a Potato Gun

1. Jan 22, 2005

### vitaly

I have to tie the construction and dynamics of a potato gun with one chapter from my physics book. That's fairly hard to do because a potato gun has much to do with more than one chapter, but my teacher just wants one... Does anybody have an idea on what the best chapter would be? I have included a list of chapters that deal with mechanics below:
• Projectile Motion
• Newton's 1st Law of Motion: Inertia
• Newtons 2nd Law of Motion: Force and Acceleration
• Newton's 3rd Law of Motioin: Action and Reaction
• Momentum
• Energy

The physics behind the potato gun lies in principles in all chapters, and I'm having a difficult time choosing the "best" one... Does anybody have an idea on which subject may have the most to do with a potato gun?

I will appreciate any help. Thank you.

2. Jan 23, 2005

### Andrew Mason

I'd go with Newton's Third Law: Action and Reaction

You have to build the gun so that the energy carried in the reaction (gun recoil) is much less than the energy of the action (potato). The energy is produced by the explanding gas in the gun barrel, which I assume would be a pipe. You have to consider conservation of momentum, but conservation of momentum is derived from the third law.

AM