How does Newton's third law not contradict his first law?

Answer 1

The applied force on the body should be more than the value of acceleration due to gravity to validate this law. Hence it should be stated in the law as

For every reaction there is an equal and opposite reaction force acting on it if the reaction force has its magnitude greater than acceleration due to gravity.

Answer 2

To describe Newton's third law of motion from Newton's second law, let us consider an isolated system of two bodies A & B mutually interacting with each other ,provided there is no external force acting on the system.

Let FAB force exerted on body B by body A. Similarly ,let FBA be the force exerted by body B on A .Suppose that due to these forces FAB & FBA, dp1/dt and dp2/dt be the rate of the change of momentum of these bodies respectively.

Then, FBA = dp1/dt ...........(i)

=> FAB = dp2/dt................(ii)

Adding equations (i) and (ii), we get,

FBA + FAB = dp1/dt + dp2/dt

or, FBA + FAB = d(p1 + p2)/dt

When no external force acts on the system, then

d(p1 + p2)/dt = 0 (zero)

=> FBA + FAB = 0 (zero)

=> FAB = -FBA ...........(iii)

Equation three is the Newton's third law of motion that is for every action there is equal and opposite reaction.

Answer 3

How DOES it contradict it? Two forces act on different objects; each of them will produce an acceleration (according to Newton's Second Law). The net force on each object is NOT zero, therefore the conditions for Newton's First Law don't apply.

Answer 4

Newton's first law states that an object at rest will remain at rest unless acted upon by an external force, while the third law states that for every action, there is an equal and opposite reaction. These laws do not contradict each other because they describe different aspects of motion. The first law deals with inertia and the absence of external forces, while the third law describes the interaction between two objects.