Question

A man pushes a block of $30kg$ along a level floor at a constant speed with a force directed at ${45}^o$ below the horizontal. If the coefficient of friction is $0.20$, then match the following.

Answer 1

{$m=30kg$,$\theta =45degree$,$\mu =\theta .20$} given

Work done by all the forces:

Work done by force of gravity = $0(\theta =90degree)$ force of gravity is perpendicular to displacement.

Work done by man on the block =$F.\cos \theta .S$ =0 because block moves with constant speed so $(F=0)$

Force=0

(Net force on the block=0) because block moves with constant speed as given in the question.