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Name: Arnol
Status: Other
Grade: Other
Location: TX
Country: United States
Date: June 2008


Question:
Does an object, say a baseball, floating inside the Space Shuttle, add weight to the shuttle? Even if it is floating and not touching anything?



Replies:
When the Space Shuttle is in steady orbit, it HAS almost no weight. Weight is the sensation of unequal aplication of force--for instance, when you stand on the ground, the sensation of "weight" is from the ground pushing up on your feet. The pull of the Earth's gravity on you is on all parts of your body equally; that does not cause the sensation of weight. When you are in free fall, you feel weightless, even though gravity pulls on you just as strongly as when you stand on the ground.

When the Space Shuttle is in orbit, gravity pulls on all parts of the Shuttle and all parts of its contents, floating or not, equally. Since there is no unequal application of force, there is no sensation of weight. In that sense, no, objects floating inside the Shuttle do NOT contribute to the Shuttle's weight because neither they nor the Shuttle have weight.

When it comes to changing the Shuttle's orbit or getting it into orbit in the first place, all objects inside the Shuttle contribute to its mass. So every baseball added to the Shuttle makes the Shuttle that much harder to accelerate. When the shuttle takes off, or when its orbit is being changed, however, it will not be weightless, because the push from its engines gives it an unequal application of force just as sitting ion the ground does. When that happens, the baseball will not be floating. It will pushing against some surface of the Shuttle.

Richard Barrans, Ph.D., M.Ed.
University of Wyoming



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