A heavy cylinder on length l is slowly taken taken out of a dense liquid. The weight felt as it is taken out of the liquid increases till attains the weight in air. Why ? What happens in this ? What is the difference between weight in air and weight of water ?

Dear Student!

When the heavy cylinder is in air, there is only a downward weight force acting on this on account of gravity. Now, when the cylinder is immersed in a dense liquid it weighs less as it experiences an upward buoyant force also apart from the downward force.

Have a look at the diagram of forces acting on a body in water.

Now, as the cylinder is taken out of the dense liquid, its weight increases since the buoyant force of air is much lesser than that of the dense liquid.

Weight in air is just due to gravity and negligibly small amount of buoyant force/ upthrust.

Weight in water lessens considerably due to substantial upthrust because of higher density of water.

I suggest you to go through the study material well to be able to appreciate the above.

Best Wishes!