Question

A man is standing still. The force by the man on the earth is \(\vec{F1}\). The force by the earth on the man is \(\vec{F2}\). Which one of the following is true?

(a) \(\vec{F1} = \vec{F2}\)

(b) \(\vec{F1} = -\vec{F2}\)

(c) \(\vec{F1} = 5(\vec{F2})\)

(d) \(2(\vec{F1}) = \vec{F2}\)

The question was posed to me in a job interview.

This is a very interesting question from Newton’s Third Law of Motion topic in division Laws of Motion of Physics – Class 11

Answer 1

The correct answer is (b) \(\vec{F1} = -\vec{F2}\)

Easiest explanation: According to the third law of motion, every action has an equal and opposite reaction. Hence every action force is equal in magnitude to its reaction but in opposite direction. Hence \(\vec{F1} = -\vec{F2}\) is the correct answer.