A student picks a box off the table and puts it on the floor.let the total work done by the student be w.one can conclude

Question

1)w>0.  2)w=0  3)w<0.  4) nothing about the sign of w

Answer 1

Work can be either positive or negative: if the force has a component in the same direction as the displacement of the object, the force is doing positive work. If the force has a component in the direction opposite to the displacement, the force does negative work.

If the student picks the box off the table and places it on the floor, they're doing negative work (w<0), because the box is going down but they're exerting an upward force, acting against gravity.

 

Answer: 3 (w<0)