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To: E. Charters who wrote (92573)1/9/2003 7:53:26 AM
From: Gabe Heti  Read Replies (2) | Respond to of 116805
 
EC said: "Gravity is tricky. Its force is proportional to the two masses, yet the acceleration is equal for any two bodies. If F did not = Mass*Accel., this would not be true. The greater mass creates a greater force, that cannot if the force is as the mass, be greater per unit mass, for any body"

Nothing strange really.

The force of gravity between two bodies = G*M*m/(R*R) (Eq. 1)

Where G is a constant, M is the mass of the larger body, m the mass of the smaller body and R the distance between their centres.

Also, F = m*a. according to Newton. So acceleration is F/m.

So the accelaration of the smaller body towards the larger body is arrived at by taking the first equation for F above and dividing it by m to give:

a = G*M/(R*R), to get the acceleration of the smaller body.

The mass of the small body disappears from the equation for acceleration, thus all bodies relative to any given M (earth) and distance (relative to the centre of the earth) will give the same acceleration. In other words, the inertia of a body cancels the effect of the larger force of gravity when acceleration is calculated.

On the moon, where M is smaller, the acceleration is smaller. At the top of Everest, where R is greater than at sea level, acceleration of a body is less than at sea level.

So nothing really mysterious at all.



To: E. Charters who wrote (92573)1/9/2003 10:16:51 AM
From: Real Man  Read Replies (1) | Respond to of 116805
 
Throw your gold bar out of the window, and the time to the moment when it reaches the ground won't depend on how expensive the gold bar is - proves Newton's gravity. The trick is to see how quickly it will vanish from the face of the Earth. But that's Chemistry. The bigger the bar is, the more quickly it will vanish, so the speed of the reaction is proportional to mass squared -g-