Question

A ball weighing 10g hits a hard surface vertically with a speed of 5 ms–1 and rebounds with the same speed. The ball remains in contact with the surface for 0.01 s. The average force exerted by the surface on the ball is

Answer 1

average force is change in momentum for unit time
the change in Momentum is 2mv because it hits and rebounds
that is 0.1 in SI units
force is equal to 0.1 /0.01
that equals 10