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### Subscribe to this site by email ## Gravity and Galileo

How Galileo gave acceleration due to gravity before Newton discovered gravity . exactly what happen Newton stated the Universal Law of gravitation and explained why objects fall to earth when dropped.

But objects were falling even before Newton explained it.

The concept of speed and velocity was known before the Law of Gravitation was formulated. ## Variation in acceleration due to gravity (g) with depth

As we go deeper from the earth suface the gravity starts decreasing but formulla is ‘F=G*m*M/r2 where distance between the object and the earth is r2 which is inversally proportional to the ‘g’ then why as we go deeper from the earth suface the gravity starts decreasing; it should be increased because distance between the earth and the object is less. but it start decreasing why?

When we go deeper into earth, the attraction at that point is due to a sphere of earth of radius (R – d) where d is the depth below the surface of earth. Let a body of mass m be kept on the surface of earth. The force exerted by earth on it,

where M is the total mass of earth and R is the radius of earth.

But,

Substituting for M,

or  (more…)

## Is the gravitational force between moon & earth are equal ? Newton’s law of universal gravitation for two bodies. This law governs gravitational forces in the Earth. (Photo credit: Wikipedia)

Is the gravitational force between moon & earth are equal ?

If the question is- “Is the force exerted by earth on moon is equal to the force exerted by moon on earth?” then the answer is “Yes

I hope that more questions will follow.

• Comparison of charge and mass ## Doubt in Law of Gravitation Newton's law of universal gravitation for two bodies. This law governs gravitational forces in the Earth. (Photo credit: Wikipedia) According to law of gravitation
F=g*(m1*m2)/r^2
If we bring two objects close to each other say our hands then the distance will be zero and the force of attraction will become infinite because r will we zero. Therefore F will become infinite but this is not the case.
When we touch our both palms together we can easily pull then away.

When we consider the distance, it is between the center of mass of the two bodies under consideration. When we bring our hands together the distance between their CM is not zero.

Other wise, the two particles under consideration must be point masses.

Then if you consider two atoms or two nuclei, the forces that come into play will be different if we decrease the distance between two atoms or nuclei. The attraction will turn into strong repulsion when the limits are exceeded. ## gravitation

the gravitational force of attraction between two objects depend on their masses and the distance between them.if so,the mass of both the objects is doubled.what change is brought about in the distance between them to ensure that the force of attraction between them does not change? ### Hits so far @ AskPhysics

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