. A 5.0-kg box is raised a distance of 2.5 m from rest by a vertical
applied force of 90 N. Find (a) the work done on the box by the applied
force, and (b) the work done on the box by gravity.
Solution
Wg = -mg d = - 5 x 9.8 x 2.5= -122.5 J
ليه اخترنا الاشاره السالبه ؟؟؟