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An observer on Earth sees two spaceships moving in opposite directions and finally they collide. At t=0 the observer on Earth says that the spaceship 1 which moves to the right with Ua=0.8c is at the point A and the spaceship 2 which moves to the left with Ub=0.6c is at the point B. The distance AB=L=4,2.10^8 m.

When do the two spaceships collide to the earth frame of reference?

What is the velocity of the spaceship 2 to the frame reference of the spaceship 1?

What is the velocity of the spaceship 1 to the frame reference of the spaceship 2?

When does the collision happen to the frame reference of the spaceship 1 and to the frame reference of the spaceship 2?

2. Homework Equations

3. The Attempt at a Solution

Let D be the point of the collision and AD=x, so DB=L-x

The velocity is constant.

spaceship 1: AD=x=0,8c.t

spaceship 1: DB=L-x=0,6c.t

By addition

L=AD+DB

L=(0,8c+0,6c).t

t=4,2.10^8/(1,4.3.10^8)

t=1sec

Is it ok so far?