# Special Relativity Spaceship Question

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1. Oct 5, 2014

### Lucille

1. The problem statement, all variables and given/known data
bob and anna are in two space ships of proper length 100m; anna's ship passes bob's and is moving in the -x dir at v=0.75c. the front of anna's ship and the tail of bob's ship coincide at x=x'=t=t'=0. bob sits at the window in his ship and sees a clock inside anna's ship
a) what position is the window in bob's space ship
b) what time does this clock in anna's ship read

2. Relevant equations
x'=gamma(x-vt)
x=gamma(x'+vt')
t'=gamma(-v/c^2*x+t)
t=gamma(v?c^2*x+t')
delta t = gamma delta to
L = Lo/gamma

3. The attempt at a solution
a)

so if bob sees the clock at the end of anna's ship, then:

L=Lo/gamma = sqrt(1-v^2/c^2)*Lo = sqrt(1-0.75^2)*(100)=66.1m <-- position of bob's window in his space ship (distance from the end of his spaceship to the window)

b)

i tried :

x=100m
v=0.75c

t'=x'/v = 4.45 * 10^-7 s

But I'm not sure if this is correct...

2. Oct 5, 2014

### Staff: Mentor

One thing that isn't clear: Bob is situated at the front of his space ship?

Chet

3. Oct 5, 2014

### Lucille

The question doesn't state that. It's asking where the window is - I'm guessing that's the point at which he can see Anna's clock, and her window is at the end of her spaceship.

4. Oct 6, 2014

### Staff: Mentor

So, under this interpretation, you are looking at the event at which x' = L0 and t = 0. In part a, you showed that $x=L_0/\gamma$. Now all you need to do is substitute this into the equation for t'.

Chet