Homework Help: Skateboard problem

1. Oct 30, 2004

guru

Matt is gliding on his skateboard at 4.00 m/s. He suddenly jumps backward off the skateboard, kicking the skateboard forward at 8.00 m/s. Matt's mass is 50 kg and the skateboard's mass is 7 kg. How fast is Matt going as his feet hit the ground?

I have no idea where to begin. Should I first find the change in momentum?

Last edited: Oct 30, 2004
2. Oct 30, 2004

BLaH!

All you have to do is use conservation of momentum:

$$p_{final} = p_{initial}$$

3. Oct 31, 2004

guru

Is this right

v_f(50kg + 7kg) = 50kg*4m/s + 7kg*4m/s
v_f = 4.49m/s ?