Materials Required:
l Tape
l String
l Coin
l Desk
Procedure:
- Tape a piece of string to one side of a coin. Tie the free end of the string to the handle on an opened desk drawer.
- Keeping the string straight, pull the coin back until it touches the front of the desk. Then release it, letting it swing away. Observe its motion. You will see that the coin travels over a shorter distance with each swing it takes.
This Is What Happens:
For any action, the energy out always equals the energy in. So, when you start the coin at the desk, it never swings higher because this would require more energy. But you suspect that the coin would travel the same distance each swing. Why does it swing lower? Energy is never lost; however, some energy changes to a different form. The act of the coin rubbing against the air is called friction, and friction changes the energy of the swinging coin into heat. The surrounding air actually becomes warmer, but this change is so slight you don’t notice a temperature increase.
