Question

What best describes the energy in a closed system at the beginning of a day and the energy at the end of the same day? Check all that apply.

Some energy can disappear after it has caused motion.
Some energy can be changed from one form to another.
Some energy can be lost to the environment around the system.
The total initial energy will be equal to the total final energy.
The total initial energy will be greater than the total final energy.
Friction can cause energy to be destroyed during the day.
Friction can cause the amount of thermal energy to increase.

Answer 1

Correct selections:
- Some energy can be changed from one form to another. (True: energy is often converted — e.g., potential → kinetic → thermal.)
- The total initial energy will be equal to the total final energy. (True for a closed system: energy is conserved, no net gain or loss.)
- Friction can cause the amount of thermal energy to increase. (True: friction converts mechanical energy into thermal/internal energy.)

Incorrect statements (why they are wrong for a closed system):
- Some energy can disappear after it has caused motion. (False: energy is not destroyed; it is conserved.)
- Some energy can be lost to the environment around the system. (False for a closed system: by definition no energy is exchanged with the surroundings.)
- The total initial energy will be greater than the total final energy. (False: total energy stays the same.)
- Friction can cause energy to be destroyed during the day. (False: friction converts energy to other forms, it does not destroy total energy.)