The universal law of gravitation determines the amount of force exerted by a constant mass (M) on another constant mass (m), separated by a distance (r), is given by the expression F = ( -GmM )/r^2

Question

a) What mathematical expression characterises the instant rate of change of the force F in respect to the distance (r) separating the two masses moving towards each other?

Answer 1

F = -GmM/r^2

dF/dt = 2GmM/r^3 dr/dt

Note that as the distance decreases, the force increases in magnitude.

Answer 2

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