# Homework Help: What is the speed of the missile, relative to ship B?

1. Mar 14, 2008

### vachan

Two spaceships, named A and B, are flying toward each other with relative speed .80c .
The captain of ship B knows that ship A uses 2-m-long missiles. She measures the length of the first missile, once it has finished accelerating, and finds it to be only 0.872m long. What is the speed of the missile, relative to ship B?
I tried to find it by L=Lo(1/sqrt 1- v2/c2)....

BUt i dont seem to find the right answer... any help i will be happy! thanks

Last edited by a moderator: Jan 7, 2014
2. Mar 14, 2008

### Staff: Mentor

Make sure you're using the correct equation for length contraction:

$$L = L_0/\gamma$$

Where:

$$\gamma = \frac{1}{\sqrt{1 - v^2/c^2}}$$