PRE-LAB: Conservation of Energy
Video Analysis of a Bouncing Ball
Answer these questions BEFORE you begin your lab work. Answer every question and do not
change any answers as you work through the lab activity. You will compare your original thoughts
with findings determined from the video analysis of this situation and include this document with your
lab report.
Situation: A ball is held approximately 2 meters above the floor and is released. It falls with
negligible air resistance and bounces 4 times. Assume that the origin is at the point
on the floor where the ball hits and that the upward vertical direction is positive.
Questions:
1. Before being released to fall, describe the ball’s kinetic, potential, and total energies.
2. What changes in the ball’s kinetic, potential, and total energies should occur while the ball is
falling?
3. Describe these energies immediately before the ball reaches the floor.
4. Draw sketches of what you think the graphs of potential energy, kinetic energy, and total energy
with time would look like as the ball is falling. Put all 3 of these on the same axes and clearly
identify each type of energy on your graph. Hint: Use your predictions in Questions 1 – 3 to help
construct these graphs.
5. As the ball rises and falls after the initial bounce, describe any changes in its kinetic energy,
potential energy, and total energy.
6. You probably would not expect the ball to bounce back to its original height. What does this mean
in terms of its energy? How would this affect the graphs of kinetic, potential, and total energies?
7. Sketch anticipated graphs of position-time, velocity-time, and acceleration-time for the ball as it
rises and falls through 4 bounces after its initial release. Remember that the origin is at the lowest
point of the fall.
8. Sketch an anticipated graph of total energy vs time for the ball falling and bouncing 4 times.
Indicate on your graph when the ball bounced.
9. Sketch what you think a graph of the net force on the ball vs time would look like during this
motion.