Experiment
Squeeze a penny through the mouth of a clear balloon. Make sure that the penny goes all the way into the balloon so that there is no danger of it being sucked out while blowing up the balloon. Blow up the balloon. When properly inflated, the balloon will be almost clear in the middle and cloudy at the area near the neck and at the end opposite the neck. The cloudiness at the ends is unstretched latex, which provides stress relief. If the balloon is completely clear all over, it is overinflated. Tie off the balloon and you’re ready to go. Grip the balloon at the stem end as you would a bowling ball. The neck of the balloon will be in your palm and your fingers and thumb will extend down the sides of the balloon. While holding the balloon palm down, swirl it in a circular motion. The penny may bounce around at first, but it will soon begin to roll around the inside of the balloon. The best orbit or path for the coin is one parallel to the floor. Once the coin begins spinning, use your other hand to stabilize the balloon. Your penny should continue to spin for 30 seconds or more.Try using different sized coins and compare how long it takes for the coin to stop spinning once you stop swirling the balloon. Does the size of the coin make any difference?
How Does It Work?
The Spinning Penny is almost like scientific poetry in motion. To understand how and why it works, you have to look at the forces that are acting on the penny. The shape of the balloon makes the penny move in a circular path - otherwise the penny would want to continue to move in a straight line. Another force to consider is friction. There's very little friction between the edge of the penny and the balloon. More friction would cause the penny to slow down and stop.The real force in action here is called centripetal force, which means center-seeking. This is a force that is always directed toward the center of the circle and is actually responsible for keeping the penny moving in a circular motion inside the balloon.
Squeeze a penny through the mouth of a clear balloon. Make sure that the penny goes all the way into the balloon so that there is no danger of it being sucked out while blowing up the balloon. Blow up the balloon. When properly inflated, the balloon will be almost clear in the middle and cloudy at the area near the neck and at the end opposite the neck. The cloudiness at the ends is unstretched latex, which provides stress relief. If the balloon is completely clear all over, it is overinflated. Tie off the balloon and you’re ready to go. Grip the balloon at the stem end as you would a bowling ball. The neck of the balloon will be in your palm and your fingers and thumb will extend down the sides of the balloon. While holding the balloon palm down, swirl it in a circular motion. The penny may bounce around at first, but it will soon begin to roll around the inside of the balloon. The best orbit or path for the coin is one parallel to the floor. Once the coin begins spinning, use your other hand to stabilize the balloon. Your penny should continue to spin for 30 seconds or more.Try using different sized coins and compare how long it takes for the coin to stop spinning once you stop swirling the balloon. Does the size of the coin make any difference?
How Does It Work?
The Spinning Penny is almost like scientific poetry in motion. To understand how and why it works, you have to look at the forces that are acting on the penny. The shape of the balloon makes the penny move in a circular path - otherwise the penny would want to continue to move in a straight line. Another force to consider is friction. There's very little friction between the edge of the penny and the balloon. More friction would cause the penny to slow down and stop.The real force in action here is called centripetal force, which means center-seeking. This is a force that is always directed toward the center of the circle and is actually responsible for keeping the penny moving in a circular motion inside the balloon.