Question

A box is pushed through 4m across a floor offering 100N resistance. How much work is done by the resistant force?

Answer 1

Force = 100N
Distance = 4m

And we know that work is done when we apply the force such that it produces displacement of the object.

So, Expression for work done,
(W) = Fscosø
ø = 180°

W = -100 x 4
= -400 J

Answer 2

               F⇒ [_Box__]<<<< ............4m
F = 100N
D = 4m
θ = 180°
W = FD cosθ
    = 100 N × 4 m × (-1)              { cosθ = cos 180° = -1}
    = -400 Nm = - 400 J