Why does an object float or sink when placed on the surface of water?

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 volume of a $500\, g$ sealed packet is $350\, cm^3$. Will the packet float or sink in water if the density of water is $1\, g\, cm^{-3}$? What will be the mass of the water displaced by this packet?

Why will a sheet of paper fall slower than one that is crumpled into a ball?

Why is the weight of an object on the moon $\frac{1}{6}^{th}$ its weight on the Earth?

You have a bag of cotton and an iron bar,each indicating a mass of $100\, kg$ when measured on a weighing machine. In reality,one is heavier than the other. Can you say which one is heavier and why?