Mechanics help...find resistive force?

Question

A cyclist starts frm rest and freewheels down a hill inclined arcsin 1/20 to the horizontal . After traveling 80m the road becomes horizontal and the cyclist travels another 80m before coming to rest without using his brakes. Given that the combined mass of the cyclist and his machine is 80kg, model the cyclist and his machine as a single particle and hence find the resistive force, assumed constant throughtout the motion.

could you explain the steps please...thnxs...

Answer 1

Potential energy converted to kinetic energy and finally equal to the work done

Pe=W
mgh=Fs
F= mgh/s
h= L sin(arcsin(1/20)= L(1/20) where L=80
F= mgL(1/20)/ s
F= 80 x 9.81 x 80 (1/20)/80
F= 39.2N