The Cork
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Originally Posted by krewat
The key was "no air resistance".
Since the bucket is falling, it is weightless, and so is the cork. It doesn't move.
Since the bucket is falling, it is weightless, and so is the cork. It doesn't move.
The cork will stay at the bottom of the bucket and not float up during the fall. A cork only floats up when the water around it is heavier and pushes it up. In free fall the water is weightless, as is the cork and bucket, so there is no force to push the cork to the top of the bucket. Neglecting air resistance, two objects of different mass and/or density will fall at the same rate (32ft/sec^2). This is true whether the cork is surrounded by the water or simply dropped beside the bucket of water.
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I don't believe it, you waskally wabbit.
<<Neglecting air resistance, two objects of different mass and/or density will fall at the same rate >>
THis is true if the bucket and the cork were falling in a vacuum side by side. But you put the cork in the bucket. There is still a difference in density, and they are in a gravitational field. The cork wants out.
<<Neglecting air resistance, two objects of different mass and/or density will fall at the same rate >>
THis is true if the bucket and the cork were falling in a vacuum side by side. But you put the cork in the bucket. There is still a difference in density, and they are in a gravitational field. The cork wants out.
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Density has nothing to do with it. Negating air resistance, all objects accelerate at 9.8 m/s. The cork and the bucket. Doesn't matter where the cork is, inside or outside the bucket it will accelerate at 9.8 m/s
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Do not confuse density with buoyancy. Density is mass per unit volume. Buoyancy is the upward force exerted on an object when it is immersed, partially or fully, in a fluid. The buoyancy value is equal to the weight of the fluid displaced by the object. Buoyancy occurs when the fluid is subjected to gravitational force but is not present in free fall. In freefall objects have no weight and therefore no buoyancy.
The cork will remain on the bottom of the bucket while in freefall.
The cork will remain on the bottom of the bucket while in freefall.
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From: KCMO
Originally Posted by sigma
...In free fall the water is weightless, as is the cork and bucket, so there is no force to push the cork to the top of the bucket...
Further, the 9.8m/s/s is the rate of acceleration due to gravity. Any other forces acting on the objects would add algebraically to that rate, which means that the cork could fall at a different rate, since it has a different combination of forces.
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Sure it does (to both statements). An object in freefall is by definition weightless. “Weight” is simply the force of gravity multiplied by the mass of the object. Without the displaced weight there is no buoyancy. The cork can rest on top of, below, beside, or inside the falling water.
The cork will remain wherever it is placed while in freefall.
The cork will remain wherever it is placed while in freefall.
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From: KCMO
Originally Posted by sigma
...An object in freefall is by definition weightless. “Weight” is simply the force of gravity multiplied by the mass of the object...
Free fall is not a case of Gravity saying to the bucket "No charge - this one's on me."
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Free fall DOES mean "weightless" - it does NOT mean "massless".
Weight and mass are two different things. Mass remains constant, weight varies with gravity.
If there is no "weight" there is no "up". So the cork doesn't move.
Weight and mass are two different things. Mass remains constant, weight varies with gravity.
If there is no "weight" there is no "up". So the cork doesn't move.
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From: KCMO
For an object to be weightless, either its mass must disappear or gravity must take a hike (or both). As long as the body has mass, and as long as it exists within a gravitational field, it has weight. Weight is a force. It is the force of gravity. It is the "F" that the "m" and the "a" conjure up.
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An object in free fall appears to be weightless. There are several examples of this. Astronauts in orbit (constant free fall) around the earth. Astronauts training in the plane nick-named the vomit comet. Both are in the earth's gravitational field but since they are in free fall appear to be weightless. So will the bucket the water and the cork appear weightless to each other. Since they are all acclerating at the same rate towards the ground, the water cannot push on the cork and make it float. As the water pushes on the cork, the cork falls away and the water falls toward it.
Last edited by 76supercab2; Dec 13, 2005 at 11:32 AM.
Laughing Gas
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From: KCMO
Please, just look up the definition in a physics book. The weightless situation experienced by astronauts is achieved by balancing the force of gravity with the centrepital force of their orbit. They don't magically make gravity disappear - they neutralize its effect.
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Originally Posted by pchristman
For an object to be weightless, either its mass must disappear or gravity must take a hike (or both). As long as the body has mass, and as long as it exists within a gravitational field, it has weight. Weight is a force. It is the force of gravity. It is the "F" that the "m" and the "a" conjure up.
Gravity is a force, that's akin to acceleration.
Go far out into space where there is no (or almost no) gravitation forces. If you accelerate your body at "1G" you will weigh what you weigh on earth. Even though there is no gravity!
Likewise, in a gravity field, if you free-fall, you will have no weight.
Mass remains constant.
Confusing, I know, but try to believe