Bowling Ball of Faith
| Physics: | Energy Transfers, Laws of Motion |
| Grade Range: | Middle School, High School |
| Format: | Stage |
THIS DEMONSTRATION IS STILL UNDER CONSTRUCTION
The Bowling Ball of Faith is easy to do, easy to setup and easy to amaze with! Be sure to practice this demonstration a few times before presenting it so you know how to stand when you let go.
Materials
- Bowling Ball with Ceiling Hook
- Wire or strong twine/string
- A Place to Hang it
Safety Precautions
Please read the Physical Demonstration section of the Demonstration Safety page before performing this demonstration.
This demonstration requires: Safety Glasses
Demonstration
- Loop the wire on a bar or hook in the ceiling of the presentation space. Give it enough slack so that, when you hang the ball from it, the ball will be about 4 feet off the ground.
- Explain to the audience that the ball is currently hanging like a pendulum, and briefly talk about pendulum motion.
- Grab the ball and pull it back, walking backwards until you can have the ball level with your face. Hold it up against your face, and ask the audience if they think it might hit you when you let go and let it swing.
- Release the ball. On the return swing, it will get close to your face, but won't hit you!
- Note: When you release the ball, make sure that you don't lean forward. Otherwise, you might end up leaning into a face tap with the bowling ball!
Why This Works
Pendulum Motion is a common topic in physics classes. When you have a weight attached to a string, you can track how it is moving and the pattern of movement quite easily. Our bowling ball is acting just like a pendulum, and so we can look at all the steps that happen during the swing. When we first let go, the ball has Potential Energy (PE), or the potential to move, due to the pull of gravity on it and the distance between its height and the lowest point of the swing. When the ball gets to the lowest point in the swing, all of the PE has been transferred into Kinetic Energy (KE), or energy of movement. When it reaches the top of the swing, the KE has now converted back to PE. But, some of the energy converts into Thermal Energy (TE), due to the friction between the loop of string and the bar on the ceiling. Since there is some energy loss from the friction, the ball will not be as high on the return swing as it was before, and won't hit the presenter!
Our pendulum can also be used to show us how Newton's Laws of Motion work.
- The first law is the law of Intertia: An object in motion will stay in motion unless acted on by an outside force. Likewise, an object at rest stays at rest unless acted on by an outside force. When we start the pendulum, we put the bowling ball in motion. The bowling ball will continue that motion, and will continue to swing on the string, until an outside force acts upon it. In this case, we know that there is friction acting on the pendulum, so over time it will eventually come to rest on its own.
- The second law is the Force Equation: a force is equal to an objects mass multiplied by the acceleration, or F=m*a.
Additional Information
- Any extra tidbits that do not fit into other sections
- This demonstration is a part of the (insert Stage Show here)