What is the distance between the astronaut and the satellite after 1.0 min?

[Patdon10]

Homework Statement

An 80 kg spacewalking astronaut pushes off a 640 kg satellite, exerting a 100 N force for the 0.50s it takes him to straighten him his arms. How far apart are the astronaut and the satellite after 1.0 min?

2. The attempt at a solution
F = Ma. Two different masses and two different accelerations. Because of Newton's 3rd law we know that the force the astronaut exerts on the satellite is equal to the force the satellite exerts on the astronaut.

F = (80)a_astronaut
a_astronaut = 1.25 m/s^2

F = 640kg(a_satellite
a_satellite = 640/100 = 0.156 m/s^2

Distance astronaut travels:
D = (1/2)(1.25)60^2 = 2250 m
D = (1/2)(.156)60^2 = 281.25 m

Total distance I got was ^ = 2531m, which is way wrong.
The correct answer is 42 m. Can anyone point me in the right direction?

 

[edgepflow]

You applied the equation: D = 1/2 a t^2.

You put in a time of 60 seconds into this formula. After 1/2 sec of initial push, are they still accelerating?

 

[Patdon10]

Ugh...what a stupid mistake. Thanks.