A 40 kg skateboarder runs at a velocity of 0.12 m/s and jumps onto a 8 kg skateboard. What's the velocity of the skateboard after the jump?

And why?

Michael E

Conservation of momentum. Momentum = velocity X mass Momentum before landing on the skateboard = 40kg X .12 m/s = 4.8 kg m/s Momentum is conserved, so the momentum after landing on the skate board will be the same Mass (after landing) = 40 + 8 kg. So 48 kg X velocity after landing = 4.8 kg m/s divide each side by 48 kg and you get velocity after landing = .48 / 48 m/s = .01 m/s