A 25Kg boy is riding a 4kg skateborad at constant velocity 3m/s . he jumos off so that his velcoity compared to the ground is now 2m/s in the opposite direction.
1- What is the velocity of the skateboard after the boy jumps off?
2- How much work didi the boy do on the skateboard?
3- If the boy exerted a force 400 N on the skatebord while he was pushing off , how long did he push for?
4- What wasa the skateboard's acceleration during that period (while the boy was pushing off )?