Consider that the room is a closed system. Ryan uses the chemical energy in his muscles to create the energy of motion. He uses this energy of motion to pull the string on the clapper of a bell to produce a sound. Sound fills the room.

Which describes the energy in this room?

A.
While energy has taken different forms, total energy remains the same.

B.
As energy changes forms, total energy decreases.

C.
As energy changes forms, total energy increases.

D.
While energy is changing forms, total energy at first increases, then decreases.

Question

Consider that the room is a closed system. Ryan uses the chemical energy in his muscles to create the energy of motion. He uses this energy of motion to pull the string on the clapper of a bell to produce a sound. Sound fills the room. 
 
Which describes the energy in this room?
 
 A.
While energy has taken different forms, total energy remains the same.
 
 B.
As energy changes forms, total energy decreases.
 
 C.
As energy changes forms, total energy increases.
 
 D.
While energy is changing forms, total energy at first increases, then decreases.

matt101 · Answer

Since this is a closed system, energy cannot enter or leave the system. That fact alone means A is the only correct answer.

All that's happening here is that energy is changing forms. It starts as potential energy stored in chemical bonds, which then becomes kinetic energy (i.e. energy of motion), and finally sound energy.