# Definition of Work

My mechanics textbook defines work such that it involves a force that is exerted as the point of application moves through some distance. I'm confused how to apply this definition.

Suppose you slide your hand across a table, such that friction exerts a force on the table but the table remains stationary due to external forces. If the work is based on the motion of the point of application, it appears that the point of application moves, so work from the hand on the table should be nonzero. However, the table has no change in kinetic energy, and external forces (for example, a static friction between the table and the floor) also exert zero work since the point of application on those external forces do not move, so the work due to the hand on the table should be 0. How do I resolve this?

• Yes, it would probably be more correct to say that work involves forces on specific particles, when those specific particles move through a distance. It's always particles moving. A "point of application" moving like in your example doesn't count, that just means which particles are primarily getting pushed is changing over time. Jan 20 at 5:23