Tim Shope
PHE 370 L
Dr. Cook
November 11, 2014
Lab #7: Work, Power, and Coefficient of Restitution
Introduction: The purpose of this lab was to learn about the coefficient of restitution by
observing the bounce height of several different types of balls when dropped, and to learn about
work and power by calculating the time that it took to run through a certain distance. This lab
will help us understand further how to calculate these different numbers and will allow us to see
power, work and the coefficient of restitution in a practical situation. It is important that we learn
about these things because it is what we have been discussing in class so this lab will help us
gain valuable information for our class as well.
Methods: In order to find work and power we first had to measure the height and depth of the
stairs that we would be running on. We multiplied the height and the depth by the number of
stairs that we would be climbing to find the total height and depth that would be traveled. Using
the total height and depth we found the displacement through the Pythagorean Theorem. Next
each of us was timed running up the stairs in seconds. We each were timed three separate times.
From this data and the weight data (in Newtons) that was calculated before the experiment we
were able to find the work that each of us did during each run up the stairs (work=distance/time).
From the work data and the time of each run we were able to find the power for each run up the
stairs (power=work/time).
To find the coefficient of restitution dropped five different type of balls from a height of two
meters and measured the height that each ball bounced. We performed this experiment on three
separate surfaces which were carpet, a wooden gym floor, and an indoor track surface. Each ball
was dropped a total of three times on each different surface and then the average height of those
three trials on each surface was calculated. From this data we were able to find the coefficient of
restitution by taking the square root of the height that the ball bounced divided by the height of
the ball when it was dropped (2 meters each time, coefficient of restitution=√height
bounced/height dropped.
Results:
Members
Mass
(kg)
Weight
(N)
Time
(s)
Height
(cm)
Depth
(cm)
Displacement (m)
Ave
Velocity
(m/s)
Work
(J)
Power
(W)
Justin
70.5
691.2
2.29
187
335.5
3.84
1.68
2654.2
1159
Justin
70.5
691.2
1.7
187
335.5
3.84
2.26
2654.2
1561.3
Justin
70.5
691.2
1.4
187
335.5
3.84
2.74
2654.2
1895.9
Dey
93.4
916.4
1.55
187
335.5
3.84
2.48
3519
2270.3
Dey
93.4
916.4
1.8
187
335.5
3.84
2.13
3519
1955
Dey
93.4
916.4
1.7
187
335.5
3.84
2.26
3519
2070
Liz
65.5
642.1
2.2
187
335.5
3.84
1.75
2465.7
1120.8
Liz
65.5
642.1
1.56
187
335.5
3.84
2.46
2465.7
1580.6
Liz
65.5
642.1
1.57
187
335.5
3.84
2.45
2465.7
1570.5
Me
72.7
711.7
1.55
187
335.5
3.84
2.48
2732.9
1763.2
Me
72.7
711.7
1.66
187
335.5
3.84
2.31
2732.9
1646.3
Me
72.7
711.7
1.77
187
335.5
3.84
2.17
2732.9
1544
4000
3500
Average Work Output
Average Work (J)
3000
2500
Justin
2000
Dey
1500
Liz
Tim
1000
500
0
1
2500
Average Power Output
Average Power (W)
2000
Justin
1500
Dey
Liz
1000
Tim
500
0
1
Carpet in Building
e (based on
Hb (cm)
Avg. Hb)
Indoor Track
e (based on
Hb (cm)
Avg. Hb)
Wood Gym Floor
e (based on
Hb (cm)
Avg. Hb)
Softball
50,54,52
0.51
0.57
12,10,20
0.26
Tennis Ball
92,90,90
130,133,1
35
0.67
0.7
0.82
80,86,87
131,130,
134
0.65
0.81
62,67,65
100,98,9
7
133,137,
138
60,63,62
0.56
73,70,72
0.6
42,45,46
0.47
61,57,57
0.54
70,73,75
0.6
35,36,38
0.43
Racquet Ball
Baseball
Batting Cage
Softball
0.81
Calculations:
Softball on Carpet:
50+54+52=156 cm, 156/3=52 cm , √52/200=.51
Softball on Track:
62+67+65=194 cm, 194/3=64.7 cm, √64.7/200=.57
Softball on Gym Floor:
12+10+20=42 cm, 42/3=14 cm, √14/200=.26
Tennis Ball on Carpet:
92+90+90=272 cm, 272/3=90.7 cm, √90.7/200=.67
Tennis Ball on Track:
100+98+97=295 cm, 295/3=98.3 cm, √98.3/200=.70
Tennis Ball on Gym Floor:
80+86+87=253 cm, 253/3=84.3 cm, √84.3/200=.65
Racquet Ball on Carpet:
130+133+135=398 cm, 132.7/3=44.2 cm, √44.2/200=.81
Racquet Ball on Track:
133+137+138=408 cm, 408/3=136 cm, √136/200=.82
Racquet Ball on Gym Floor:
131+130+134=395 cm, 395/3=131.7 cm, √131.7/200=.81
Baseball on Carpet:
60+63+62=185 cm, 185/3=61.7 cm, √61.7/200=.56
Baseball on Track:
73+70+72=215 cm, 215/3=71.7 cm, √71.7/200=.60
Baseball on Gym Floor:
42+45+46=133 cm, 133/3=44.3 cm, √44.3/200=.47
Batting Cage Ball on Carpet:
61+57+57=175 cm, 175/3= 58.3 cm, √58.3/200=.54
Batting Cage Ball on Track:
70+73+75=218 cm, 218/3=72.7 cm, √72.7/200=.60
Batting Cage Ball on Gym Floor:
35+36+38=109 cm, 109/3=36.3 cm, √36.3/200=.43
Conclusion: In regards to the data that was found on average work we can see that Dey had the
highest average work followed by myself, then Justin, then Liz. When looking at the data that
went into this calculation which is weight (N) and the displacement in meters we can see that
weight was the key factor to the amount of work done since the displacement that each of us
traveled was equal. When looking at the average power data we can see that weight once again
plays a large role in the amount of power that is done. The equation for power is power=
work/time. Each of us mad it up the stairs in about the same amounts of time so the thing that
really varied the data was the average amount of work that was done. Also from this equation we
do see that if the time that it takes to move through the distance increases then the amount of
work will decrease. We can see this on Justin’s first trial. He had a time of 2.29 seconds so his
power output was much less in that trial.
For the coefficient of restitution experiment we can see clearly that the racquet ball will have the
highest coefficient of restitution on all of the surfaces. We can also see that the indoor track
surface was the surface that allowed for the highest bounce and therefor the highest coefficient of
restitution values for each different ball. This surface must provide for the most elastic collision
between the surface and the ball. Another thing that we can conclude from this data is that some
of the balls interact much differently on different types of surfaces. For example, the softball has
a coefficient of restitution of 0.51 and 0.57 on the carpet and the indoor track respectively, but on
the wooden gym floor the coefficient of restitution is just 0.26. The baseball and the batting cage
softball acted similarly to the softball but the racquet ball and tennis ball had fairly consistent
coefficients of restitution on each surface.