Newton's Third Law of Motion Help?

Question

I don't understand how an object can move if the object is pushing me back with equal force when I push it. Please explain.

Answer 1

Newton's third law is the law of acceleration. When forces are equivalent in opposite directions, there exists no acceleration. When forces are equivalent in directions other than opposite, the object will continue on an acceleration path.

Answer 2

When there is equal (E) but opposite (O) force, the sum of the forces is f = (E - O) = 0 because E = O. And when f = 0 = ma; a = 0 because m > 0. Therefore there is no acceleration.

Now, for the tricky part...acceleration a = dv/dt by definition; where dv means a change in velocity and dt is the time elapsed (change) while the velocity was changing. Let's look at that change in velocity.

dv = v1 - v0; where the velocity changes from v0 to v1. Thus when v1 <> v0, we have dv <> 0; that is, there is some non-zero magnitude and/or direction in that change. [Remember velocity has both magnitude and direction.] Thus, from a = dv/dt <> 0, we show that there is non-zero acceleration.

But, and this is the big BUT, what if velocity is constant? What's dv then? Well, dv = v1 - v0 and when v1 = v0, meaning the velocity is constant, we have dv = v0 - v0 = 0. So from dv/dt = (v0 - v0)/dt = 0/dt = 0 = a. There is no acceleration when v = constant.

But wait...v can be any constant. It could be light speed v = c = 300,000 kmps for example. Yet a is still = 0 = dv/dt. And when f = (E - O) = ma = 0, we have a = 0. That is to say, v can be any velocity, just so it is constant and a, your acceleration will be zero when there is equal but opposite force. And when that happens, there is no net force for you to feel.

So there you have it, your object is moving at a constant velocity, but there is an equal but opposite force between you and the object. In many cases, that force will simply be your weight (E) which is offset by your chair's opposite force (O).

For example, if you are sitting in your car going along at a constant v = 60 kph, you feel only the weight of your back pressed again the seat cushions, which are pushing back with a force equal to your weight. But if you suddenly accelerate, the net force (f = ma) adds to your back weight (E) and you feel the increase in the push back (O) by the cushions.

Answer 3

Newton's Third Law: For every action, there is an equal and opposite reaction.

"A force is a push or a pull upon an object which results from its interaction with another object. Forces result from interactions! As discussed in Lesson 2, some forces result from contact interactions (normal, frictional, tensional, and applied forces are examples of contact forces) and other forces are the result of action-at-a-distance interactions (gravitational, electrical, and magnetic forces). According to Newton, whenever objects A and B interact with each other, they exert forces upon each other. When you sit in your chair, your body exerts a downward force on the chair and the chair exerts an upward force on your body. There are two forces resulting from this interaction - a force on the chair and a force on your body. These two forces are called action and reaction forces and are the subject of Newton's third law of motion. "

It describes the interaction of two objects.

The fact that you can walk is an example of this third law actually.

You exert a force on the ground and the ground pushes back the same force so you can walk!

Answer 4

If we swim on water we pushes the water in the backward side in certain force and the water pushes us in the forward direction in equal and opposite force

Answer 5

'what u need to understand is, there is no time elapse between you pushing the object and it's reaction on you. it is a SIMULTANEOUS combo, so WHILE u r pushin it, it pushes u back.

'i hope i have answered ur doubt...just think abt it a bit