Question

Rather than ascribing the increased kinetic energy of the stone to the work of gravity, we now (when using potential energy rather than work-energy) say that the increased kinetic energy comes from the ______ of the _______ energy.

Choose the best answer to fill in the blanks above:

a) work / potential
b) force / kinetic
c) change / potential

Answer 1

C) change / potential

Step-by-step explanation:

Rather than using work-energy theorem, we will use the energy conservation.

If the work of gravity is present in the system, we can say that the stone is falling.

So, the energy conservation is

`K_1 + U_1 = K_2 + U_2`

Since the kinetic energy is increases, that means the final potential energy must decrease in order to keep the total mechanical energy constant. Furthermore, if the stone is falling, we can say that the potential energy of the stone is decreasing.

So, the correct expression should be:

The increased kinetic energy comes from the change of the potential energy.