# Exploding Boat

1. Oct 28, 2004

### k3l

hi all,
i am just wondering... if there is a guy has to jump off a small boat (u know... those have no engine, and etc... just a small wooden boat) which is stay stationary in calm water and is about to explode (for some reason... ). so yeh, that guy has to jump off the boat from one of the side. Which side should he jump off from in order to achieve the longest distance? and why?

Last edited: Oct 28, 2004
2. Oct 28, 2004

### BobG

Assuming the explosives are in the boat, the best way to the most distance between him and the boat is to jump off the back.

Thanks to conservation of momentum, the net will be zero. In other words, however much momentum the person converts to velocity is balanced by momentum imparted to the boat. Both move opposite directions with the lighter object moving further in a given amount of time.

$$v_{boat}m_{boat}-v_{man}m_{man}=0$$

That only works in a frictionless environment. In practice, the water will slow the boat's velocity more than the air will slow the man's velocity, so the best option is too make sure the boat will moves with as little resistance as possible.

You might note that if the man jumps off the side, the resistance provided by the keel of the boat against the water will allow the man to jump further, but the resistance of the keel also means the boat continues to slow even after the man has left. The net distance between the two will be less even if the man's absolute distance was greater.

In other words, pushing the boat away from the man is more important than how far the man can jump.

It's always important to be prepared for anything, eh? :rofl:

3. Oct 28, 2004

### k3l

ahaha, yeh
thank you very much for the answer :D

4. Oct 28, 2004

### k3l

why is the minus sign there? instead of plus?
thx