Two Basic Types of Energy

Clara Williams Douglass Middle Math & Science Academy
543 N. Waller
Chicago IL 60644
(312) 534-6176

Objective:

Students will make pendulums to identify potential and kinetic energy.

Materials Needed:

mousetrap ball string pencil eraser

Strategy:

1. Set the mousetrap. Drop the pencil eraser on the release lever.
2. Drop the ball and let it come up a few times. Describe one full bounce,
from the top of the bounce to the bottom, and back to the top, in terms of the
preservation of kinetic and potential energy.
3. Tie the eraser to the string. Hold the end of the string, and swing the
eraser, like a pendulum. Describe one full swing, back and forth, in terms f
the presence of kinetic and potential energy.

Conclusion:

When the mousetrap is set, the presence of the loaded spring gives it
potential energy. At the moment the spring is released, the potential energy
is converted to kinetic energy, or moving energy. Great care should be taken
to assure that fingers are not injured by the mousetrap.
As the ball is held above the floor, it has potential energy. When the
ball is released, the potential energy is changed to kinetic energy as the ball
falls toward the floor. When the ball strikes the floor, it is compressed, and
the kinetic energy is changed to potential energy. The potential energy in the
rubber propels the ball into the air, again converting the potential energy to
kinetic energy. Some of the energy escapes in the form of heat as the ball
meets resistance with the air and the floor. Thus, the height of the cycle
decreases as the ball bounces.
The swinging pendulum passes through a cycle similar to that of the
bouncing ball. All the energy contained in the system is potential energy at
the instant the pendulum is all the way to the top on either side of the
cycle.At the moment the pendulum is at the bottom, moving neither upward nor
downward, all the energy is kinetic.
If the pendulum is at rest, it has neither potential nor kinetic energy.
When in a position that gravity can cause movement when released, it has
potential energy.

Performance Assessment:

1. Teacher observation.
2. At completion of the lessons, students will be able to answer questions.

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