Name(s) ________________________________________________ Date _________________ Period _____
Ball Rolling Experiment Discussion
Directions:
Use the data table, the graphs, the information below, and your Lab Manual Notes to answer the questions on
the following pages.
Background Information
According to Newton’s Laws of Motion, objects move because of unbalanced forces acting upon them.
There are forces pulling and pushing all objects from a variety of directions. Some forces hold objects in place,
other forces cause objects to speed up and still other forces slow objects down. In order to calculate the effect
of forces on an object, the formula of force equals mass times acceleration can be used. When an object is
rolling down a ramp, three major forces are acting on it: gravity, friction, and drag.
Gravity is an attractive force between two objects that all objects with mass both produce and feel. In
the equation from the first paragraph, the acceleration of objects in a free fall or rolling down a ramp is caused
by gravity. The magnitude of the force of gravity an object experiences depends on two factors: its mass and
the distance it is away from the other object. The object that produces the strongest gravitational force that we
experience every day is Earth itself. As the distance between two objects gets larger, the force of gravity they
experience gets smaller. This is why astronauts experience very low gravity conditions in space, but we are
pulled very strongly downward when we try to jump here on Earth. The mass of an object also plays a factor in
the force of gravity it experiences. The more mass an object has, the greater the force of gravity it experiences.
This is why bubbles blown by a child, which have a very low mass, float in the air for a long period of time, but
people, which have a much higher mass, are not able to float at all.
Friction is a force that opposes motion and is caused by the contact between two objects. The reason it
opposes motion is because every time one object comes in contact with another, a small amount of energy is
lost in the collision. Over time, enough energy is lost through this contact that the object slows down and
eventually stops. Friction is the reason why the pencil you roll across your desk when you’re bored in class
does not continue rolling forever. It is also the principle at work when you hit the brake pedal in a car. Pressing
that brake pedal puts the brake pads in contact with the rotors the wheels are attached to. The friction created
by the contact between the brake pad and the rotor takes energy away from the car and slows it down. Two
significant factors that play a role in the amount of force friction produces are the mass of the object and its
surface area. As the mass of an object increases, the amount of friction also increases because each of the
collisions between the two objects releases more energy. Think about getting hit by a bubble (low mass) or
getting hit by a person (high mass), and which would feel like a greater force on you. The surface area is also
important to consider because the more surface area an object has, the larger the amount of that object will be in
contact with the other object. More surface area means more contact, more contact means more friction, which
means a more rapid slowing of movement.
Drag is another force that opposes motion and is caused by the contact between an object and a fluid. A
fluid is a substance in a liquid or gas form. The most common type of drag is commonly referred to as wind
resistance and is caused by objects coming in contact with the air around them. You have probably seen the
effects of this force watching weather reporters try to stand while being knocked around by hurricane force
winds, or watching the faces of skydivers gets smushed and stretched oddly as they freefall. The amount of
drag an objects experiences depends greatly on the fluid it is travelling through. The higher the density of the
fluid, the more drag force an object experiences. This is why it is much easier to walk through air (low density
and little drag) than it is to walk through water (higher density and higher drag). In addition to the fluid it is
moving through, the surface area and volume of the object itself can greatly affect the amount of drag force it
experiences. Increasing the surface area and volume of an object also increases the amount of drag on the
object. The reason for this is very similar to the reason why friction is increased with additional surface area.
There are simply a larger number of collisions between the air and the object when the object is larger. Each of
these collisions causes the object to lose energy and slow down.
Data Table
Mass
(g)
Surface Area
(cm2)
Volume
(cm3)
Mean Speed
(ft/s)
Median
Speed
(ft/s)
Range Speed
(ft/s)
Basketball
544.10
1633.13
6205.88
8.82
8.83
0.62
Volleyball
272.20
1320.25
4510.87
8.45
8.53
0.83
Golf ball
46.00
55.42
38.79
10.35
10.34
1.50
Bouncy ball
165.00
3739.28
21500.86
5.61
5.68
0.88
Softball
182.15
277.59
434.89
8.70
8.74
1.43
Field hockey ball
150.40
149.57
172.01
9.99
9.98
1.24
Nerf ball
371.35
1372.28
4780.11
8.57
8.63
0.93
Superball
16.90
36.32
20.58
9.89
9.85
1.58
Soccer ball
416.60
1520.53
5575.28
8.17
8.22
1.13
Marble
1.60
3.14
0.52
9.84
9.84
1.70
Ping pong ball
2.45
47.78
31.06
4.70
4.84
1.95
Tennis ball
55.55
149.57
172.01
8.50
8.54
0.67
Graph 1:
Graph 2:
Graph 3:
Discussion Questions:
1. According to the background information on the first page, what is the name of the force that causes the
balls to roll down the ramp? ____________________________________________________________
2. According to the background information on the first page, what is the name of the force caused by the
contact between the ball and the ramp/floor that slows the ball down? ___________________________
3. According to the background information on the first page, what is the name of the force caused by the
contact between the ball and the air that slows the ball down? _________________________________
4. According to the background information on the first page, how does an object’s mass affect the force of
gravity on it? ________________________________________________________________________
____________________________________________________________________________________
5. According to the background information on the first page, how does an object’s mass affect the force of
friction on it? ________________________________________________________________________
____________________________________________________________________________________
6. According to the background information on the first page, how does an object’s surface area affect the
force of friction on it? _________________________________________________________________
____________________________________________________________________________________
7. According to the background information on the first page, how does an object’s surface area affect the
force of drag on it? ___________________________________________________________________
____________________________________________________________________________________
8. According to the background information on the first page, how does an object’s volume affect the force
of drag on it? ________________________________________________________________________
____________________________________________________________________________________
9. Calculate the slope (rounded to the nearest ten thousandth) of the best fit line on the mass graph from 0 g
to 500 g.
Y1 value
X1 value
Y2 value
X2 value
Slope Calculation
Slope Answer
(w/ proper unit)
10. What type of correlation do mass and rolling speed show in graph 1? ___________________________
11. Calculate the slope (rounded to the nearest ten thousandth) of the best fit line on the surface area graph
from 800 cm2 to 2900 cm2.
Y1 value
X1 value
Y2 value
X2 value
Slope Calculation
Slope Answer
(w/ proper unit)
12. What type of correlation do surface area and rolling speed show in graph 2? ______________________
13. Calculate the slope (rounded to the nearest ten thousandth) of the best fit line on the volume graph from
0 cm3 to 21,000 cm3.
Y1 value
X1 value
Y2 value
X2 value
Slope Calculation
Slope Answer
(w/ proper unit)
14. What type of correlation do volume and rolling speed show in graph 3? _________________________
15. Based on your answers to questions 9 and 10, fill in the blank in the following statement. As the mass
of the ball increases, the speed at which it rolls ______________________________________________.
16. Using the background information from the first page, explain why mass has the effect on speed you
said it did in question 15. ______________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
17. Based on your answers to questions 11 and 12, fill in the blank in the following statement. As the
surface area of the ball increases, the speed at which it rolls ___________________________________.
18. Using the background information from the first page, explain why surface area has the effect on speed
you said it did in question 17. ___________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
19. Based on your answers to questions 13 and 14, fill in the blank in the following statement. As the
volume of the ball increases, the speed at which it rolls _______________________________________.
20. Using the background information from the first page, explain why volume has the effect on speed you
said it did in question 19. ______________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
21. Based on the slopes you calculated in questions 9-13 and the information below, estimate the speed you
would expect a Bowling Ball and Physioball to roll if they were tested in our experiment. Round your
estimates to the nearest tenth.
Bowling Ball
Estimated Speed
Physioball
 Mass = 7272 g
 Mass = 963 g
 Surface area = 1466 cm2
 Surface area = 17,671 cm2
 Volume = 15,830 cm3
 Volume = 220,893 cm3
Estimated Speed
22. Would the data support or reject the following hypothesis? ____________________________________

If the mass, surface area, and volume of a ball are all increased, then the speed it rolls will also
increase because larger balls will have a greater amount of momentum, which will cause them to
roll faster.
23. According to the data, what would the answer to the following purpose question be? _______________
____________________________________________________________________________________

Which of the mass of a ball, the volume of a ball, or the surface area of a ball has the greatest
effect on the speed a ball rolls?
24. In the original lab procedure, we had several people timing each ball roll. Explain why this is a better
idea than having one person time each roll. ________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
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25. In each graph, the ping pong ball is an outlier (doesn’t follow the pattern the other dots do) and has the
highest range. Explain why the ping pong ball might not have rolled the same way the other balls did.
____________________________________________________________________________________
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26. In this experiment, we measured or calculated distance, time, speed, mass/weight, surface area, and
volume as part of either the independent or dependent variables. What are the only two properties from
page 6 of your Lab Manual Notes that we did not measure or calculate in this experiment? __________
____________________________________________________________________________________
27. How could the results of this experiment be used to improve a product or activity that does not involve
sports or sporting equipment? Identify the product/activity and explain your response. _____________
____________________________________________________________________________________
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