Two are easy :)
Force down = m g, does no work, no motion up or down
Force up from floor = m g, also does no work
The third is easy too
work done by input force = +185 * 7.5
= + 1388 Joules
Now the negative one, the friction force which is opposite to motion
F = - mu m g = - .23 * 48 * 9.81
= - 108 Newtons
Work = - 108 * 7.5 = -812 Joules
You put more in than the friction took out, so the box accelerates
A 48-kg box is being pushed a distance of 7.5 m across the floor by a force Upper POverscript right-arrow EndScripts whose magnitude is 185 N. The force Upper POverscript right-arrow EndScripts is parallel to the displacement of the box. The coefficient of kinetic friction is 0.23. Determine the work done on the box by each of the four forces that act on the box. Be sure to include the proper plus or minus sign for the work done by each force.
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