Taylor Jordan and Lauren Cawthon
Title: Uniform Circular Motion Exploration
Purpose: To study the motion of objects moving in a circle with constant speed.
Materials:
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Balloon
Pennies
Bucket
Water
Spring-wound toy car
Bubble level
Procedures:
A. Coin in a Balloon: Blow up a clear balloon with a penny inside the balloon. Once the
balloon is inflated, hold it at the bottom and move it in small quick circles. Observe the
penny once it is rolling around the wall of the balloon.
B. Bucket of Water Trick: Fill a bucket of water and swing it in a vertical circle at constant
speed.
C. Scorcher Chamber: Place a spring-wound car on the side wall of a bucket, near the
bottom. With the car parallel to the bottom of the bucket, launch the car by giving it a
push.
D. Bubble Level Accelerometer: Hold the bubble level parallel to the floor with the bubble
in the center of the glass tube. Then, accelerate the level to the right and slow down.
Observe the bubble responds when you change your speed. Now hold the bubble level
perpendicular to your body and have your lab partner observe the bubble as you spin in a
circle.
Analysis and Conclusions:
Coin in a Balloon
1. What force keeps the coin moving in circles?
Centripetal force keeps the balloon moving in a circle. Centripetal force is a force that acts on a
body moving in a circular path and is directed toward the center around which the body is
moving.
2. Describe the motion of the coin if the balloon were to break.
If the balloon broke, which it did with our group, the penny would fly away in a roughly straight
path. Without the centripetal force, the coin no longer stayed in a uniform circular motion.
Bubble Level Accelerometer
3. Does the bubble move in the direction of the acceleration or in the opposite direction?
The bubble moves in the opposite direction of the acceleration. If we accelerated to the right, the
bubble moved to the left and vice versa. As the level slowed down, the bubble shifted towards
the direction it was accelerating in.
4. How does the bubble respond to your spinning?
When the bubble is spinning perpendicular to your body it stays on the side of the level closest to
your body and does not move. This is the result of the centripetal force pulling the bubble
inwards towards the center of mass.
5. Based on what you know about the response of the bubble to acceleration, do objects
moving in a circle experience an acceleration? If so, describe the direction of the
acceleration.
Objects in a circle are constantly undergoing acceleration because the direction of their velocity
is constantly changing even though the object(s) are moving in a uniform circular motion.
Bucket of Water Trick
6. Describe the behavior of the water as the bucket moves in a circle.
As we moved the bucket in a circle, the water stayed in place for each full circle. If we kept the
bucket in uniform circular motion, they water seemed to push back into the bucket, keeping it
from spilling.
7. Explain what would happen to the water if the bucket were to stop directly over your
head.
If the bucket stopped directly above someone’s head, the water would begin to fall straight down
onto that person’s head. The water would fall because the forces of uniform circular motion no
longer apply if the object is not moving in a circle any longer. There would be no centrifugal
force keeping the water inside the bucket if it were to stop at the top of the circle, so that person
would end up getting wet.
8. As you rotated the bucket in the vertical circle, where did the bucket feel heaviest?
Lightest? Explain your observations.
The bucket felt the heaviest at the top of the circle, and it felt the lightest at the bottom of the
circle. This is because of the centripetal force acting on the bucket. This is the force keeping the
bucket on a circular path and pulling it towards the center. At the top of the circle, the force of
gravity and the centripetal force are both acting on the bucket, making if feel heavier.
Scorcher Chamber
9. Describe the motion of the car once it is released.
Once we released the car, it traveled around the inside of the bucket on a circular path. As it
continued to go around inside of the bucket, it slowed down while dropping closer to the bottom
of the bucket with every circle. When the car hit the bottom of the bucket, it stopped all motion
fell into the bottom of the bucket, upside down.
10. Suggest an explanation for the car’s motion.
The centrifugal force of the car kept it pressed against the walls of the bucket until car ran out of
power and fell to the bottom because of gravity. The centrifugal force is what kept the car going
in a circle, and the force of gravity stopped the motion and brought the car to the bottom of the
bucket.