Purpose
The feather and penny demonstration shows how air resistance affects falling objects. A penny and feather are in a tube, and when the tube is flipped, the feather takes more time to fall than the penny. But when the air is evacuated from the tube, both fall in the same way.
Parts
- Vacuum pump
- Tube containing feather and penny
The vacuum pump is located beneath shelf C1 (and it’s surprisingly heavy to pick up). The tube is in between shelves C and D up against the wall.
Setup and How it Works
In front of the class, turn the tube upside down and show that the penny falls faster than the feather. Then, put the vacuum hose over the bottom of the tube.
Turn on the vacuum (it needs to be plugged in) and wait until you hear most of the air evacuated, this should take about 30 seconds. Close the valve (which looks like a metal switch next to where the hose connects to the tube), and disconnect the hose. The valve can be stiff and difficult to turn, so if you’d rather, leave the hose connected and ignore the valve. Flip the tube over, and show students that the feather and penny now fall in the same way.
Note: Sometimes the feather gets stuck at the end of the tube. Usually, this means the penny gets a head start, and you just need to flip the tube over again. If it really gets stuck, try letting the air out. If all else fails, unplug the hose and manually reach in to free the feather.