1C20.10 • Uniform Acceleration: Penny and Feather
Location: Floor Demo + Floor Cabinet
Photo shows the demonstration used at the University of Texas at Austin.
Concepts Conveyed:
- In a vacuum, objects falling from the same height will reach the ground at the same time regardless of mass and shape.
- Under normal conditions, air resistance affects the rate at which the objects fall.
Instructions / Notes:
- Demonstration apparatus includes a plastic tube containing a penny and a feather at rest at one end of the 100 cm tube.
- Before creating the vacuum, quickly invert the tube to the opposite vertical alignment to demonstrate that the penny and feather fall at different rates.
- After the objects are at rest, connect the tube to the vacuum pump. It takes less than 1 minute to pump air out of the tube.
- Close the valve/petcock and disconnect the hose and repeat the inversion, as before, noting the difference in descent.
Vacuuming out the tube:
- Connect the red hose to the vacuum valve by tightening the clamp around the nozzle, as seen in the picture above.
- With the vacuum valve in the parallel open position, turn on the vacuum pump using the power switch. Leave pump running for about 30 seconds.
- Close the valve by moving it to a perpendicular closed position before turning off the pump and disconnecting the hose.
- To allow air back into the tube, return the valve to the open position.
Demo Staff:
- Clamp tube stand to table.
- OPEN VALVE: valve knob is PARALLEL to the vacuum hose and to the tube.
- CLOSED VALVE: valve knob is PERPENDICULAR to the vacuum hose and to the tube.
- Make sure to ask the instructor if they want the tube in vacuum prior to rolling out.
Last updated on February 18, 2025