Energy is added or removed from a system only if work is done. If no work is done, the energy is just transferred from one kind to another.

1. An object is dropped.

   1.   ?    Added
   2.   ?    Removed
   3.   ?    Transferred

2. An object is lifted up.

   1.   ?    Added
   2.   ?    Removed
   3.   ?    Transferred

3. An object speeds up.

   1.   ?    Added
   2.   ?    Removed
   3.   ?    Transferred

4. An object is slowed down.

   1.   ?    Added
   2.   ?    Removed
   3.   ?    Transferred

5. A moving object stops by compressing a spring.

   1.   ?    Added
   2.   ?    Removed
   3.   ?    Transferred

6. A spring is compressed slowly.

   1.   ?    Added
   2.   ?    Removed
   3.   ?    Transferred

7. A spring is released slowly.

   1.   ?    Added
   2.   ?    Removed
   3.   ?    Transferred

8. An object is lowered to the ground.

   1.   ?    Added
   2.   ?    Removed
   3.   ?    Transferred

9. An object stops due to friction.
   

   1.   ?    Added
   2.   ?    Removed
   3.   ?    Transferred

10. An object starts moving.

    1.   ?    Added
    2.   ?    Removed
    3.   ?    Transferred

11. An object is thrown up.
    

    1.   ?    Added
    2.   ?    Removed
    3.   ?    Transferred

12. A compressed spring is released and causes an object to move.

    1.   ?    Added
    2.   ?    Removed
    3.   ?    Transferred