# Homework Help: Relative snake problem

1. May 12, 2008

### happytimes

A relativistic snake, 1 meter long, travels in a velocity of 0.6c on a table. A boy is about to strike two axes the same time on each side of the snake (1 meter gap between the axes). The boy figures, that if the axe at the back strikes right behind the snakes "tail", the snake will not be hit thanks to the length contraction.

as in:
|-----------____|

While the snake, who figures what the boy is about to do, is a bit worried. The snake see the axes approach with a velocity of 0.6c, and hence is contracted and the gap seem less than 1 meter.

as in:
|-------|---

The question is; what will happen?

Will one axe hit the snake, which is what the snake assumes?
Or will the snake make it between the axes, as the boy believes?

2. May 12, 2008

### yuiop

If the axes bounce very fast off the table after striking it the snake will not be touched by the axes

It simply a case that the boy sees the axes hit the table at the same time while the snake sees the axe nearest his head hit the table first (and bounce out the way) and the axe nearest his tail hits later after his tail has safely passed through. Its all about the the "relativity of simultaneity".

3. May 14, 2008

### tiny-tim

Welcome to PF!

Hi happytimes! Welcome to PF!
Yes … the boy says that the axes are always at the same height, but the snake says that the front axe is always lower than the back axe.

You can easily check this from the Lorentz equations.