Question

Roy pushes a box of mass 16.6 kilograms across a floor by exerting a horizontal force of 99.1 newtons. The coefficient of kinetic friction between the box and the floor is 0.324, and Roy pushes the box 11.4 meters. What work does friction do? Include units in your answer. Answer must be in 3 significant digits.

Answer 1

We found the friction earlier, the friction has a magnitude of 52.71 N.

Now, we know that the work is given by:

`W=Fd`

but this is the formula for when the forces and displacements are colinear and point in the same direction; in this case the friction points in the opposite direcion of the displacement, then the work the friction does has to be negative. Plugging the values we have that:

`W=52.71\cdot11.4=600.8`

But as we said this work has to be negative. Therefore we conclude that the work done by the force of friction is -601 J (rounded to 3 significant digits)