Bouncing Ball Lab
Your name
Partners:
Partner #1
Partner #2
Purpose:
We will study a bouncing ball by intentionally
changing the drop height to see what happens
to the return height.
8 September 2015
Apparatus & Procedure:
ball
meter stick, mounted on wall
floor
software--Logger Pro
ball
drop height
return height
1. Mount meter stick on wall.
2. Make sure you have a clear space to drop and recover the ball.
Make sure there is space for observers to place themselves on “eye level” with the return height.
3. Hold the ball at a height of 0.10 meters.
4. Record your drop height. Rest your hand on the wall; do not move your hand.
5. Release the ball by opening your fingers. Do not move your hand.
6. Your partner, who is on eye level with the return height, measures the return height of the ball.
Reminder, this person should be looking for the “bottom” of the ball, and should estimate between the
lines for their measurement. Record the return height.
7. Increase the drop height by 0.10 m. Repeat steps 4-6.
8. Repeat steps 4-7 until you have ten values for the drop height, up to and including 1.0 meters.
9. Make a graph of Return Height vs. Drop Height.
Data Table & Calculations:
Sample Calculations of Return Height—
For each drop height, take the average of the two return heights:
Return Height:
0.059m + 0.061m = 0.060m
2
0.145m + 0.135m = 0.140 m
2
Table of Results:
Graphical & Mathematical Analysis:
Vertical Intercept, -0.0113 m:
Slope: 0.859 m/m
When the Drop Height is 0 m, the Return
Height is –0.0113 m.
This means that for every 1.0 meter
increase in Drop Height, there is a 0.859
meter increase in Return Height.
This is confusing: It means that a ball that
is held in contact with the ground (0m drop
height) would be released and then bounce
such that the bottom of the ball would be
0.0113 meters below the floor.
Realistically, we would expect that a ball
released from ground level would have
zero return height.
This seems to indicate that the ball always
returns to a height that is lower than the
drop height.
Correlation very close to 1.000—indicating that a linear fit is a good representation of the points.
The slope-intercept form of a line is
y = mx + b
R = (m) D + (b)
R = (0.859 m/m) D + (-0.0113 m)
zero, by
10% rule
R = (0.859 m/m) D + 0 m
Conclusions:
(a)
From analysis of the graph of Return Height vs. Drop Height, the line that best represents the
points can be written as
R = ( 0.859 m/m ) D + ( 0m )
Since a line is does the best job of representing the pattern in our graph,
we conclude that Return Height and Drop height are directly proportional:
(b)
When comparing our graph to the graphs created be other groups, it was observed that each of the
graphs had different slopes. Each group also had a different ball to be dropped—i.e. golf ball,
racquetball, lacrosse ball, ping-pong ball, etc.
It was observed that all slopes had values between “0” and “1”, and that they all had units of
“meters / meters”.
The ball with the best bounce was the golf ball—the graph generated by the group that used the
golf ball had the largest slope. The ball with the “worst” bounce was the tennis ball—the graph
generated by the group that used the tennis ball had the smallest slope.
New terms:
defn Coefficient of Bounciness,
 slope of a Return Height vs. Drop Height graph.
 will tell you the return height to drop height ratio for a certain type of ball.


(c)
A Coefficient of Bounciness of “1.0 m/m” means that, the return height will equal the drop
height. This is rare.
A Coefficient of Bounciness of “0.0 m/m” means that, no matter what the drop height, the
return height will always be zero. An example would be a wad of clay: no matter the drop
height, the wad will “stick” to the ground and not bounce.
The greatest source of error in this lab would be the measurement of return height: After the ball
rebounds, it only comes to rest momentarily before falling to the ground again. The person
measuring the return height must make their observation—including an estimate of how far
between the lines—very quickly. Even a skilled observer would have difficulty measuring the
drop height.