Question

When an object is allowed to slide down a hill it stops at the point B because of friction. If friction force depends only on the normal component of the reaction force with coefficient of friction variable along the path. The work done in taking the object slowly from B to A along the hill will be –

• A. mgh
• B. 2 mgh
• C. > 2 mgh
• D. < mgh

Answer 1

Answer: (B)

2 mgh

Answer 2

W_g + W_Fr = DK

W_g = – W_Fr

$\mathrm { W } _ { \mathrm { Fr } } = - \mathrm { mgh }$

W_f + W_g + W_f = Dk

W_f = – W_g – W_Fr

(W_F = 2mgh)