Question

There is a spring attached to the screen door on Elijah's front porch. Elijah opens the door stretching the spring<(1) after walking through the doorway<(2) Elijah lets go of the door and the spring contracts pulling the door shut.<(3) describe an energy transformation that took place in each of the number events above.

(1)
(2)
(3)

Answer 1

By opening the door, Elijah is using the chemical energy, which he obtained from eating food to do work. Thus, he is converting chemical energy to mechanical energy.
Stretching the spring by opening the screen door convert the potential energy which is stored in the spring to kinetic energy.
Overall there is conversion of chemical energy to potential energy.
By letting the door go, Elijah is using chemical energy. By snapping shut, the door is converting potential energy to kinetic energy. The overall energy change is conversion of chemical energy to kinetic energy.