Why Objects Float Or Sink When Placed On The Surface Of Water

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

A dry clean steel needle of diameter d and density rho when carefully placed on the surface of water remains floating . If T is the surface tension of water , then maximum value for the diameter d of the needle for enabling it to float will be

A point source of light is placed at a depth of h below the surface of water of refractive index mu . A floating opaque disc is placed on the surface of water so that light from the source is not visible from the surface. The minimum diameter of the disc is

Ice floats on the surface of water because

Assertion: A needle placed carefully on the surface of water may float. Reason: A needle placed carefully on the surface of water may float due to the surface tension as upward forces due to surface tension balances the weight of the needle.