# Special Relativity Spaceship Question

Lucille

## Homework Statement

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

## Homework 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

## 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...

## Answers and Replies

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

Chet

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.

Mentor
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.
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
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