What do you mean by buoyancy?

What do you mean by free fall?

Amit buys a few grams of gold at the poles as per the instruction of one of his friends. He hands over the same when he meets him at the equator. Will the friend agree with the weight of gold bought? If not,why? [Hint: The value of $g$ is greater at the poles than at the equator.]

The volume of $50\, g$ of a substance is $20\, cm^3$. If the density of water is $1\, g\, cm^{-3}$,will the substance float or sink?

Calculate the force of gravitation between the Earth and the Sun,given that the mass of the Earth $= 6 \times 10^{24} \, kg$ and of the Sun $= 2 \times 10^{30} \, kg$. The average distance between the two is $1.5 \times 10^{11} \, m$.

The earth and the moon are attracted to each other by gravitational force. Does the earth attract the moon with a force that is greater or smaller or the same as the force with which the moon attracts the earth? Why?