Conservation of Energy - Video Analysis of a Bouncing Ball
A good way to study energy conservation is to examine the behavior of a bouncing ball. Using VideoPoint2.5, precise locations of a ball as it repeatedly bounces can be determinedat every 1/30 sec increment. You can use this dataand the mass of the ball to precisely calculate the net force on the ball and the ball’s velocity, acceleration, kinetic energy, potential energy, and total mechanical energy at any time during the trip.
Directions:
1. Use VideoPoint2.5 to open the video
titledbouncingball.
2. Mark the position of the ball in each
frame as it fallsand bounces 4 times.
3. Use the meter stick in the background
toscale the video frames.
4. Place your origin at the ball’s position
whenit hits the floor (lowest position
marked on the video).
5. Change the mass of the ball to 302 grams.
9. Now make one graph showing kinetic, potential, and total energies, again using the y-
component. These should all be graphed on the same set of coordinate axes. You may wish to
change the colors of the plotted points. Copy and paste this graph in the box below.
10. Construct a graph of net force-time on the ball. Paste the graph in the box below.
Questions and Discussion:
1. What happens to its kinetic energy as the ball rises and falls after a bounce?
2. What happens to its potential energy as the ball rises and falls after a bounce?
3. What happens to its total mechanical energy as the ball rises and falls after a bounce?
4. What is represented by the abrupt “gaps” in the total energy plot?
5.Find the approximate percentage of total energy that was conserved during each of the
bounces (divide the approximate total energy after a bounce by the approximate total energy
before the bounce).
Does there appear to be a fairly constant percentage of energy conserved in each bounce?
7. You know why the vertical “sections” of each graph gets shorter, but why does each “section” of
the graph also get shorter horizontally?
8. What is the net force on the ball:
as it rises?
as it falls?
during the first bounce?
during the second bounce?
during the third bounce?
9. What is the acceleration of the ball:
as it rises?
as it falls?
during the first bounce?
during the second bounce?
during the third bounce?
On a separate page:
A.Make statements comparing your pre-lab predictions with your actual findings.
B. Describe important concepts that can be gained/learned from analyzing these graphs.
Generate questions and provide answers toat least3 important concepts related to each of
your5 graphs (at least 15 total questions and answers)
Example: (Q): Why is the velocity-time graph comprised of straight line segments?
(A): the ball had a constant acceleration of g while in the air, both rising and falling
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