# State the universal law of gravitation and derive its expression.

The universal law of gravitation states that the force of attraction between two masses m_{1} and m_{2} separated by a distance r is directly proportional to the product of the masses and inversely proportional to the square of the distance between the masses.

That is,

F α m_{1}m_{2}

F α 1/r^{2}

Or, F = Gm_{1}m_{2}/r^{2}

Where, G is a constant called the universal gravitational constant and is equal to 6.67 × 10^{-11} Nm^{2}/kg^{2}

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