Question

A girl pushes a load of mass 20kg to a distance of 10 metres in 5 seconds calculate (1) the work done (2) the energy used (3) the girl's power (a=g=10m/s square)

Answer 1

I assume no friction, so the thing is accelerating
F = m a
F = 20 a
a = F/20

distance = (1/2) a t^2
10 = .5 * a * 25
a = 20/25 = 4/5 = .8 m/s^2

so F = 20 a = 160 Newtons

(1) work = 160 * 10 = 1600 Joules

(2) that work is the enegy used

(3) power = energy/time = 1600/5 = 320 Watts

Answer 2

30watts