Question

In which of the following cases, the net force acting on the body is not zero?

• A. An object floating in mercury
  
• B. A ball freely falling from a certain height
• C. A cork floating on the surface of water.
• D. All of the above cases.

Answer 1

The correct option is B A ball freely falling from a certain height

In the case of falling freely under gravity.

By newton second law

$F_{net}=ma$

in this case $a=(-g)$

Hence there is net force in downward direction.

Rest are all balanced.