# Length Contraction

1. Jul 19, 2012

### sklotz

1. The problem statement, all variables and given/known data

A spaceship moves past you at speed v. You measure the ship to be 300 m long, whereas an astronaut on the ship measures a length of 356 m. Find v.

2. Relevant equations

L=L1sqrt(1-v^2/c^2)

3. The attempt at a solution

I have tried this by using the above formula. I plugged in 300 for L and 356 for L1 and I have tried it the other way as well where I plug in 300 for L1 and 356 for L. The answer is in terms of c. I only have one try left and dont understand what Im doing wrong.

2. Jul 19, 2012

### TSny

You are looking for v in terms of c, which means that you are trying to find v/c. So, let x = v/c and write your equation as L = L1sqrt(1-x^2). Show us some of the details of how you would solve this for x.

3. Jul 19, 2012

### sklotz

L/L1=sqrt(1-x^2)
(L/L1)^2=1-x^2
1-(L/L1)^2=x^2
x=sqrt(1-(L/L1)^2)

4. Jul 19, 2012

### TSny

Good. That should you get you the correct answer.