A 4kg box is compressed 50cm on a spring (k=800 N/m) and then slides across a horizontal floor. If (u=0.4) between the box and the floor...

A) how much work is done?
B) assuming the frictional force is constant, how far will the box slide before it comes to a stop?

1 answer

A)
The elastic potential energy stored in the spring would convert into KE of the box. This KE would be dissipated while working against the frictional force.
So work done = (1/2)Kx^2
= 800*0.5^2/2
= 100 Joules
B)
Frictional force F= mu*mg
F = 0.4*4*10 = 16 N

Work done = F*d
d = 100/16 = 6.25 m