a boy of mass 43.2 kg runs and jumps onto a stationary skateboard. The boy lands on the skateboard with a horizontal velocity of 4.10 m/s. The skateboard has a mass of 2.50 kg.
Using ideas about conservation of momentum,calculate the combined velocity of the boy and skateboard just after the boy lands on it.
(Pls explain. I've got my physics exams very soon)