Amazing displays of ignoranceSandettie Light Vessel Automatic tells us: "My dad's friend told us there's no such thing as gravity - it's just the weight of air holding us down". Tell us of times you've been floored by abject stupidity. "Whenever I read the Daily Express" is not a valid answer.
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Scaryduck LIKES EGG, Thu 18 Mar 2010, 16:48)
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Force=mass x accelerationWhere Acceleration = rate of change of speed
Is one of Newton's laws. A more accurate way of writing it would be to say that force is rate of change of momentum, and momentum is the mass of an object multiplied by its velocity.
The key word here is velocity. "Speed" says nothing about the direction that something is moving in: in mathmatical jargon it's called a 'scalar' - a value that only has one property. Velocity is what's known as a 'vector' because it doesn't just depend on how fast something is moving, it depends on the direction it is moving in too.
It follows that if something is moving in one direction and a given speed and is shifted so that it is moving in a different direction at a given speed its momentum will have changed - exerting a force on the object.
This is a slightly long-winded way of saying that any object moving in a circle is constantly changing momentum and as such has a force constantly acting on it. In this case, centrifugal force. This is what keeps the water in the bucket.
(P.S. Please, please don't tell me that centrifugal force doesn't exist, and it's all centripetal. You teachers may have told you this, but they lied.)
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MatJ LOOK, Thu 18 Mar 2010, 18:22,
2 replies)
My explanation was far more technical."The water's trying to fly through the bottom of the bucket and away from your shoulder, not being attracted to your shoulder which is the what's spinning. If your shoulder was the centre of the earth and we were water, we'd all try to fly away from the ground, not stick to it." Or words to that effect, with a few hiccups in between. He just looked at me funny.
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baw__bag contains traces of nuts on, Fri 19 Mar 2010, 20:44,
closed)
hmmcentrifugal force is just a shorthand way of saying the acceleration (f=ma) is due to things spinning about in a rotational kind of manner. There's no such thing as a force specific to spinny things as such.
I hate grammar nazis, and now I'm a inertia nazi.
AN inertia nazi. Damn.
(, Mon 22 Mar 2010, 21:29, closed)
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