PHYSICS DOUBT- Isaac Newton's 3rd law of motion.

Question

Sir Isaac Newton's third law of motion states that to every action there is an equal and opposite reaction, and it happens in 2 different bodies and not the same body, so if the action and reaction force dont act on the same body, and thus don't cancel out each other then why don't we fall into the Earth's core, as the normal force won't be able to cancel our weight..?

Answer 1

In this situation we have two bodies: the person and the Earth. The Earth acts on the person with the force of gravitational attraction that we call weight. Its magnitude W = mg. The person acts on Earth with the force of gravitational attraction F = G mM / R². Those two forces are equal in magnitude. If you compare them, you can see that g = GM / R². Actually, not only the person falls on the Earth, but the Earth also "falls" on the person. We do not see this fall only because the mass of the Earth is 10 ²² times greater than the mass of an average person. As a result, acceleration of the Earth's "fall" is negligible.

The person is not falling into the Earth core because the surface, which acts on the person with normal reaction force, prevents this from happening. BTW, according to the Newton's third law the person also acts on the surface, and we call this force apparent weight.

Again let me stress: normal reaction force and weight act on a body and if the body is not moving, they cancel each other. But apparent weight applied to the surface or scale and is not cancelled by weight. Weight is a gravitational force and is the same at a given location. Apparent weight is an electromagnetic force and could vary.