# Homework Help: Movement High School Physics

1. Jul 5, 2006

### MetalCut

I just want to know if this is correct.
The question is:
A boy and a girl on a skateboard push each other away at 30N for 1.2 s
The boys' mass is 45kg and the girl's mass is 40kg.

Determine the velocity after they have stopped pushing each other?
How far did the girl move while their hands were touching?

BOY Girl
F=30N F=30N
m=45kg m=40kg
a=0.6666m/s/s a=0.75m/s/s

Now to get the velocity, do i use v=v0+at, im not sure.
So for the boy then v=0+(0.66666)(1.2)
v=0.79m/s
And for the girl then v=0+(0.75)(1.2)
v=0.9m/s

And for the displacement of the girl: = v0t+(0.5)(0.75)(1.2)^2
= 0.54m

2. Jul 5, 2006

### Hootenanny

Staff Emeritus
Looks good to me

3. Jul 5, 2006

### MetalCut

Thanx man.
I appreciate.

4. Jul 5, 2006

### Staff: Mentor

Looks OK to me. An easier way to find the velocities after they stop pushing is to use the impulse/momentum theorem. (Look it up.)

Also, realize that we are talking about the movement of their center of masses. (The boy and girl are deformable objects.)

5. Jul 6, 2006

### MetalCut

Thanx man. I will do that.