Question

I take an empty can and pierce a hole near it's bottom and cover the hole with an adhesive tape. Now I fill the can with water and stretch a balloon over the mouth of the can. Now I take the can over the sink and take off the tape covering the hole. The balloon caves in. Why does this happen?

Answer 1

A liquid has mass and is attracted by the force of gravity. This weight, or force, acts downwards on the base of the container which holds the liquid. So when the tape covering the hole is taken off, water will be coming out of the can. As a result the pressure inside the can goes on decreasing and the inside and outside pressure of the can is not balanced. So the ballon caves in due to air prssure acting on it.