1. Makenna Cooper, Lukas Binau, Savannah Sharp, Alexis Lundy
Rotational Motion
Makenna Cooper, Lukas Binau, Savannah Sharp, Alexis Lundy

2. Background Information
Rotational motion is the movement of a body about its center of mass. While Circular Motion is very similar to Rotational Motion, they are not the same. The center of mass of an object is the average position of all the parts of the system, weighted according to their masses. (Khan Acadamy, 2015.) Rotational motion depends on several things: torque, inertia, and angular velocity. These three things are what help us determine what the rotational motion of an object is.
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3. Hypothesis
I hypothesize we can demonstrate rotational motion by rolling a ball down a ramp.

4. General Statement of how you will conduct the demonstration.
For this experiment, we will use a tennis ball and a ramp made from a book, and roll the ball down the ramp.

5. Materials Needed
1. Ball
2. Ramp (20 cm)

6. Procedure
1. Set up materials by placing the ramp on an even surface and measuring that the top of the ramp is 20 cm tall.
2. Place the ball on the top of the ramp.
3. Roll the ball down the ramp by carefully pushing it, until it begins to roll by itself.

7. Safety Precautions 1. Do not let the ball bounce around the room.
2. Be sure to stop the ball after the experiment is complete.

8. Analysis
When we rolled the ball down the ramp, it began to rotate. It also began to accelerate the longer that it traveled down the ramp.

9. Conclusions
The ball began to rotate due to the friction between the ball and the ramp. This caused the ball to rotate around its center of gravity.

10. Evaluation
Yes, we were able to demonstrate rotational motion by rolling a ball down a ramp.

11. Major Concepts
Rotational motion is motion around an object's center of mass where every point in the body moves in a circle around the axis of rotation. The center of mass is the point in an object from which there is an equal amount of mass in any two opposite directions.

12. Historical Perspective
Ever since men discovered that throwing rocks with a spin allowed them to be more accurate when killing animals, we have been using rotational motion. Archimedes had the first principle of a lever as well as contributions of Galileo who was studying the planetary system and later Newton.

13. Application of Concepts
Rotational motion can be observed when a pitcher throws the ball, when the wheels of a car turn, or during an ice skaters spins.

14. Review Answers
1. Force exerted on an object is a push or pull, whereas torque exerted can be thought of as a twisting motion on an object.
2. The lever arm is the perpendicular distance from the axis of rotation to the line of action of the force.
3. Perpendicular.
4. They are equal.
5. If you try to bend over to touch your toes and extend your center of mass beyond your support base, you will create a torque that topples you.
6. Along a line that passes through the center or mass.
7. An object that is rotating will continue to rotate unless acted upon by a net torque.
8. Mass and distribution of mass.
9. A pendulum with a longer string has a lower frequency than that with a shorter string. This means it will swing fewer times before coming to a stop.
10. When your legs are bent, they have less rotational inertia.

15. Review Answers 2 11. They would have the same acceleration.
12. A solid hoop would have greater acceleration.
13. By changing the shape of his or her body.
14. Rotational velocity is rotational speed plus direction.
15. Linear momentum is the inertia of motion and angular momentum is the inertia of rotation.
16. It causes the wheel to move in a circular path.
17. The “inertia of rotation” of a rotating object, equal to the product of rotational inertia and rotational velocity.
18. Unless a net torque acts on a rotating system, the angular momentum of an object is constant.
19. It will double.
20. The angular momentum is unchanged. His speed will increase while he tucks and decrease when he straightens out.

16. Answers
1. It’s easier to use a longer screwdriver because it has a bigger torque.
2. The mass of the rock is 1.5 kg
3. 2 kg
4. Longer feet would help.
5. Having your arms out when balancing helps you because you have more rotational inertia, giving you more time adjust
6. If the bowling ball has a diameter that is the same as the volleyball, the volleyball will have a greater acceleration. Because the formula of rotational inertia of a ball is I=2/5mr^2, “I” is the rotational inertia, “m” is the mass, “r” is the diameter, so when the bowling ball has more mass than the volleyball, it will has a greater rotational inertia. When the object has a greater rotational inertia, it will be harder to get rolling.

17. Answers (2)
7. To provide greater angular momentum, and through that angular momentum, there is greater stability when the disk is spinning.
8. Because its better aerodynamically and your place your hand further down on the football when u throw it
9. w = 3.00 rotations per second
10. The rate of rotation decreases. By re-distributing the mass of the rotating system in a manner of spreading it out, you increase the rotational inertia of the system. Angular momentum, the product of rotational inertia and rate of rotation, must remain constant as per a conservation law, unless a net external torque acts on the system. Since rotational inertia increases, the spin rate must decrease