Item 19 A student pushes a box across a rough horizontal floor. If the amount of work done by the student on the box is 100 J and the amount of energy dissipated by friction is 40 J, what is the change in kinetic energy of the box

60 J

Explanation:

Given,

Work done to push the box = 100 J

Energy dissipated by friction = 40 J.

According to work energy theorem work done is equal to change in kinetic energy.

Change in Kinetic energy = Work done by student + Work done by friction

Change in Kinetic energy = 100 J - 40 J

Work done by the friction will be negative because it will act in opposite direction of force applied.

Change in Kinetic energy = 60 J