Explain why it is easier to lift a stone under water than in air.

What is a submarine? How can it be made to dive in water and come to the surface of water?

A cork piece floats on water surface while an iron nail sinks in it. Explain the reason.

Which of the following will sink or float on water? (Density of water = 1 g cm^-3)

1. Body A having density 500 kg m^-3
2. Body B having density 2520 kg m^-3
3. Body C having density 1100 kg m^-3
4. Body D having density 0.85 g cm^-3