Question

In which of the following cases the net force is not equal to zero?

• A. A kite skillfully held stationary in the sky
• B. A ball falling freely from a height
• C. A helicopter hovering above the ground
• D. A cork floating on the surface of water

Answer 1

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

According to newton's 1st law of motion, A body maintains its states ie Rest or motion with uniform velocity until and unless there is no external force apply on that.

So, A kite skillfully held stationary in the sky, A helicopter hovering above the ground, A cork floating on the surface of water, All these examples are maintaining state of rest so resultant or net force on it will be zero.

A freely falling ball have acceleration that will equal to $g$ So, Net force on it will not be equal to zero.