Hi I've been told that Newton's 3rd law says that every action has an equal and opposite reaction. How then does anything move? I mean that if say something pushed to the right with such a force then an equal force shall push back to the left and cancel things out, including the movement or displacement. hmm. The situation is identical from any angle. Is this a paradox? Probably not because i'm typing this! (or am I? ha ha)
PS My engineering teacher just laughs when I try to explain it to him. Is he mad or am I?

>Hi I've been told that Newton's 3rd law says that every
>action has an equal and opposite reaction.

You should not rely on hearsay. You can do some reading too.

>How then does
>anything move? I mean that if say something pushed to the
>right with such a force then an equal force shall push back
>to the left and cancel things out, including the movement or
>displacement. hmm. The situation is identical from any
>angle. Is this a paradox? Probably not because i'm typing
>this! (or am I? ha ha)

Right. This is a good thought. It's a pity you did not stop to ponder it. To give you another chance, I'll type my answer way below.

>PS My engineering teacher just laughs when I try to explain
>it to him. Is he mad or am I?

I do not know. Have you seen your psychiatrist lately?

 

 

 

 

 

 

 

 

 

 

 

 

 

The action and reaction act on different bodies. When a billiard ball bumps into another one, it stops, because of the reaction of the latter that starts moving, because of the action of the former.

How can you say that the motion of the second billiard ball is
an OPPOSITE reaction? It's in the same direction.

>How can you say

I can't.

>that the motion of
>the second billiard ball
>is
>an OPPOSITE reaction? It's in the same direction.

That's correct.

>Hi I've been told that Newton's 3rd law says that every
>action has an equal and opposite reaction. How then does
>anything move? I mean that if say something pushed to the
>right with such a force then an equal force shall push back
>to the left and cancel things out, including the movement or
>displacement.

Ahhhh, but when we start talking about movement and displacement, Newton's 1st and 2nd laws come into play and the important thing about them is that they apply to the *external* forces exerted *on* a single object. The classic example of the N3 (Newton's 3rd) dilemma is the horse and cart - when the horse pulls the cart, the cart exerts an equal and opposite force on the horse, so how do they move?

Now if we look at the horse (that is define our single object to be "horse"), the external forces acting on it include the force exerted on the horse by the cart and frictional forces between the horse and the ground, but it *does not* include the force of the horse pulling the cart because that is a force exerted *by* the horse and not *on* the horse.

But if we define our single object to be "horse + cart", the force exerted on the cart by the horse and on the horse by the cart are ignored when looking at the motion of the system because they are now *internal* forces. The only forces we worry about now are external ones such as friction which are acting on the "horse + cart" object.

Hope that helps

Amanda