Hi Jyoti, 

It depends on the context of the problem. If liquid is non-viscous & moving with respect to container and flow of liquid is streamline, then we apply Bernoulli's equation.

Example, 

Water is kept in a bucket. A small hole is made at the bottom. Find speed of water coming out of the hole.

It depends on the context of the problem. If liquid is non-viscous & moving with respect to container and flow of liquid is streamline, then we apply Bernoulli's equation.