Newton’s universal law of gravitation :
- Every object in the Universe attracts every other object with a definite force.
- This force is directly proportional to the product of the masses of the two objects and is inversely proportional to the square of the distance between them.
- G = constant of proportionality = Universal gravitational constant.
- The value of G was first experimentally measured by Henry Cavendish.
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- If the mass of one object is doubled, the force between the two objects also doubles.
- Also, if the distance is doubled, the force decreases by a factor of 4.
- If the two bodies are spherical, the direction of the force is always along the line joining the centres of the two bodies and the distance between the centres is taken to be d.
- In case when the bodies are not spherical or have irregular shape, then the direction of force is along the line joining their centres of mass and d is taken to be the distance between the two centres of mass.
- The centre of mass of an object is the point inside or outside the object at which the total mass of the object can be assumed to be concentrated.
- The centre of mass of a spherical object having uniform density is at its geometrical centre.
- The centre of mass of any object having uniform density is at its centroid.