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Step 18Operation and video
There are four stages to this demonstration and each will be broken down into a series of step by step instructions.
Free fall in atmosphere
1) Open all three toggle valves and disconnect the hose from the manifold.
2) Unscrew both of the locking bolts. The apparatus is now free to rotate.
3) Grasp one of the handles and quickly rotate the whole apparatus 180 degrees.
4) Watch and listen for the thud as the aluminum disk lands first while the paper floats down.
5) Repeat a couple times to show that air resistance always causes the paper to land second.
Creating the vacuum
It helps to screw in one of the locking bolts to keep the apparatus in place during this stage.
1) Connect the hose to the vacuum manifold.
2) Turn on the vacuum pump.
3) Watch the vacuum gauge change as the air is removed from both tubes.
5) Wait until the gauge reads -76 cmHg. Remember, this is relative to atmosphere (76 cmHg) so the actual pressure in the tubes is close to (but still slightly above) 0 cmHg.
6) Close all three toggle valves, turn off the vacuum pump, and disconnect the hose from the manifold.
Because the vacuum gauge is on the low pressure side of the cart/base plate toggle valve, it will read the same pressure as the tubes.
Free fall in vacuum
1) Unscrew the locking bolt that kept the apparatus upright. The apparatus is again free to rotate.
2) Grasp one of the handles and quickly rotate the whole apparatus 180 degrees.
3) Watch and listen as both objects always land simultaneously.
4) Repeat a couple times to verify the effect.
Repeat at atmosphere
1) Open the toggle valves to the tubes and listen to the air rush back in. Watch as the rushing air blows the paper disk upwards.
2) Repeat the experiment at atmosphere. The paper again lands second.
When completely finished, screw in both locking bolts to secure the apparatus and open the cart/base plate toggle valve.
Free fall in atmosphere
1) Open all three toggle valves and disconnect the hose from the manifold.
2) Unscrew both of the locking bolts. The apparatus is now free to rotate.
3) Grasp one of the handles and quickly rotate the whole apparatus 180 degrees.
4) Watch and listen for the thud as the aluminum disk lands first while the paper floats down.
5) Repeat a couple times to show that air resistance always causes the paper to land second.
Creating the vacuum
It helps to screw in one of the locking bolts to keep the apparatus in place during this stage.
1) Connect the hose to the vacuum manifold.
2) Turn on the vacuum pump.
3) Watch the vacuum gauge change as the air is removed from both tubes.
5) Wait until the gauge reads -76 cmHg. Remember, this is relative to atmosphere (76 cmHg) so the actual pressure in the tubes is close to (but still slightly above) 0 cmHg.
6) Close all three toggle valves, turn off the vacuum pump, and disconnect the hose from the manifold.
Because the vacuum gauge is on the low pressure side of the cart/base plate toggle valve, it will read the same pressure as the tubes.
Free fall in vacuum
1) Unscrew the locking bolt that kept the apparatus upright. The apparatus is again free to rotate.
2) Grasp one of the handles and quickly rotate the whole apparatus 180 degrees.
3) Watch and listen as both objects always land simultaneously.
4) Repeat a couple times to verify the effect.
Repeat at atmosphere
1) Open the toggle valves to the tubes and listen to the air rush back in. Watch as the rushing air blows the paper disk upwards.
2) Repeat the experiment at atmosphere. The paper again lands second.
When completely finished, screw in both locking bolts to secure the apparatus and open the cart/base plate toggle valve.
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