5. Stas is pushing his car which has broken down. He does 3KJ of work against friction
and moves it a distance of 12m. How big is the friction force he has to push against?

6. Sam is a pole-vaulter who has a mass of 80kg. He vaults to a height of 4m.
a) How much work does he do?
b) How much kinetic energy will he have just before he lands?
c) When he lands, his trainers compress by 1cm. Calculate the average force acting
on his trainers as he lands.