National Science Standards
See videos on-line: free-fall.
Advance Preparation Time
Get a Styrofoam or paper cup.
Earth-orbiting spacecraft experience a condition described as weightlessness. The spacecraft is in a state of free-fall as it orbits. If the spacecraft has astronauts on board, the astronauts are able to move about with ease because they too are in a state of free-fall. In other words, every thing in their immediate world is falling together. This creates the weightless condition. Crew members and all the other contents of the spacecraft seemingly float throughout the air.
On earth, momentary weightlessness can be created in a number of ways. Some amusement parks achieve a second or two of weightlessness in certain wild high-tech rides. A springboard diver feels a moment of weightlessness at the top of a spring just as the upward motion stops and just before the downward tumbling motion to the water below begins. As the diver falls, friction with the air quickly offsets the weightless sensation and produces drag that returns at least a portion of the diver's weight before the water is struck. NASA eliminates the air friction problem and achieves about 30 seconds of weightlessness with a special airplane. High above Earth, the plane begins a long arc-like dive downward at a speed equal to the acceleration of a falling object. After 30 seconds, the plane pull out of the dive and climbs back to the high altitude to begin another weightless cycle.
The airplane's skin and engine thrust during the dive totally negate air friction on the people and experiments in the plane.
For a moment the falling cup demonstrates weightlessness (or zero-g). Before the cup is dropped the water pours out of the cup freely. While the cup is falling, the water remains inside the cup for the entire fall. Even though the water remains inside, it is still attracted to Earth by gravity and ends up in the same place that the water from the first experiment did.
Punch a small hole in the side of the cup near its bottom.
Hold your thumb over the hole as you fill the cup with water. Ask students what will happen if you remove your thumb.
Remove your thumb and let the water stream out into catch basin on the floor.
Again seal the hole with your thumb and refill the cup. Ask students if the water would stream out of the hole if you drop the cup.
Drop the filled cup into the catch basin. The demonstration is more effective if you hold the cup high before dropping it.
You may video the demonstration and then use the slow motion controls on the playback machine to replay the action. You may also want to show also weightless videos.
Illustration is by Leyla Sezen.
Author: Tugrul Sezen BACK TO COURSE MAIN PAGE
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