When will two ships collide in reference frame of Earth?

[matt14690]

4. Two ships are moving toward each other with velocity of 0.7 c. At time zero in reference frame (reference
frame of Earth), Ship 1 nearly collides with Earth and Ship 2 is at the distance of 105 km from Earth.
(a)How long does it take according to the clock on Earth before the ships collide? What are the coordinates
of each ship at the collision?
(b)The clock in reference frame where Ship 1 is always at origin and at rest is set to zero when Ship 1 nearly
collides with Earth. What will the clock in show when the two ships collide?

 

[matt14690]

Can't figure this out

 

[Doc Al]

4. Two ships are moving toward each other with velocity of 0.7 c.

Is that the speed of each ship with respect to the Earth?

 

[merryjman]

Aren't you supposed to demonstrate that you've at least attempted to solve the problem? If you can't even start, try explaining what you do know about the problem.