# Force and Simple Dynamics: Pushy Astronaut

1. Jan 28, 2009

### mrnastytime

1. The problem statement, all variables and given/known data
An astronaut of mass 65 kg pushes off a satellite of mass 420 kg, exerting a force of 120 N for the 0.94 s they are in contact.

2. Relevant equations
What is the speed of the astronaut after they have separated?
Ans: 1.84 m/s
What is the speed of the satellite after they have separated?
Ans: .268 m/s
How far apart are they after 1 minute?
d=??? m

3. The attempt at a solution
This is my attempt. I used the position as a function of time formula:
$$x = x_0 + v_0 t + (1/2) a t^2$$
For the astronaut: x= 0+0+.5(1.84 m/s^2)(60 s)^2= 3312 m
For the satelite: x= 0+0+.5(.268 m/s^2)(60)^2= 513 m
In order to get the separation, i subtracted the two and got 2799 m. But this is incorrect according to my online homework program. did i make a mistake or use the wrong formula?

2. Jan 28, 2009

### rl.bhat

What is the speed of the astronaut after they have separated?
Ans: 1.84 m/s
What is the speed of the satellite after they have separated?
Ans: .268 m/s

How did you get these two values?

3. Jan 29, 2009

### mrnastytime

accelration of satelite=F/m=120N/420kg=0.285m/s^2
accelration of astronaut=F/m=120N/65kg=1.84 m/s^2

To find velocity, i used the velocity as a function of time equation:
V=V0+at

astronaut: V=0+1.84 m/s^2(0.94s)=1.74 m/s
satelite: V=0+0.285 m/s^2(0.94s)=0.268 m/s