As an object moves from point A to point B only two forces act on it: one force is nonconservative and does −30 J of work, the other force is conservative and does +50 J of work. Between A and B,
A) the kinetic energy of object increases, mechanical energy decreases.
B) the kinetic energy of object decreases, mechanical energy decreases.
C) the kinetic energy of object decreases, mechanical energy increases.
D) the kinetic energy of object increases, mechanical energy increases.
E) None of the above.

Question

Quizplus · Accepted Answer

The net work done on the object is +20 J (50 J from the conservative force minus 30 J from the nonconservative force), which increases the kinetic energy. However, the mechanical energy decreases because the nonconservative force does negative work.

As an Object Moves from Point a to Point B