Is there anyone else out there that thinks that Newton's 2nd law of Physics is just plains stupid?

Question

I can't wrap my head around the idea that my chair is pushing me back. Or the walls are pushing against the celing and the floor.

Answer 1

You mean Newton's 2nd law of motion, don’t you?

Force = mass * acceleration

I like this law, a lot, actually.
It may not seem very intuitive at first to someone trying to learn it, but with practice, you'll come to understand.

The basic concept is that a [net] force applied to an object causes it to accelerate. When you push on something, it moves. They key work being a "net" force. If there is no net force (i.e. F = 0), there is no acceleration.
The force the chair is exerting on you, called the "Normal" force is necessary because while you are sitting in the chair are you falling towards the ground? No, of course not.

We all know that Earth (gravity) exerts a force on you in the downward direction, called "Weight". Without a balancing force, you would continue to accelerate downward. If the chair did not exert a normal force back upward to cancel weight, there would be a net force acting upon you in the downward direction which would cause you to accelerate downward.

A similar case is true for other objects, like when you push on a wall. In this case, it is not gravity which exerts the force, you are doing it. In order to keep the wall from accelerating when you push on it, the wall must exert a force back which is "normal" to its surface. Eventually, however, the wall will not be able to provide ample normal force to counter your push and parts of the wall will begin to accelerate as the wall breaks.

Answer 2

You mean Newton's Third Law: for every action there is an opposite and equal reaction.

Don't worry, Newton himself had a hard time with this one at first, but it makes perfect sense and helps explain a lot of things.

For example:
Why does a gun recoil when you fire it? The gun pushes the bullet, the bullet in turn pushes the rifle in the opposite direction. Thankfully, the gun and person are much more massive than the bullet, so the recoil speed is much much smaller than the speed of the bullet.

How do rockets move in space? The rocket's combustion chamber pushes the gas out the exhaust, and the exhaust pushes the rocket in the opposite direction.

How do you walk across the floor? You push on the floor, the floor pushes you in the opposite direction, which is what propels you forward. When you try walkin on ice, this Law becomes that much more apparent.

Why do you hurt your hand when you hit the wall? You hit the wall, but the wall hits your hand back with the same force.

Why do you lean back when pulling say a wagon or something by a rope? Because if you were to pull while standing straight up, you would fall towards the wagon. You pull wagon, and it might move towards you, but the wagon pulls you pack, which is why you would move forward.

I think one thing that is hard to grasp is this: If the force is equal and opposite, why don't they cancel, and nothing moves? The trick here is the fact forces only cancel when acting on the same object.

With the wagon exampe: you pulled the wagon and the wagon moved. Your force only affected the motion of the wagon. The wagon pulled you back, which is why you would move forward as well, but that force only affects you. Those two forcs act on two objects, not the same one, so they don't cancel.

Answer 3

Nope. It makes perfect sense. If something DOESN'T exert a force back, then it MOVES. Why? Because YOU MOVED IT.

Let me give you an example: Let's say you sit in a chair. Let's say that a scale is under the chair. Well, did you put force on the chair? Yes, the scale tells you the force (in the form of weight). If the chair wasn't against something that pushed back, you would fall right to the ground.

Ok, now let's say your chair is in mid air. Does the air push back? Not enough to keep you up. Don't believe me? Try it yourself.

Peace and axle grease,
Jon

Answer 4

My Friend, if your chair was not pushing you back, how do you suppose its still there suppoting you ? Whenever you push or pull something, unless there is an equal force in the opposite direction, it will move.

That's not Newton's Law, that's how things work. Newton was smarter than the rest and put it don as a law.

Answer 5

Well, think about it. If your chair was not exerting any pressure to keep you up, you'd be sitting on the floor with a chair squashed under you. If you were sitting on the floor with no opposite force you'd be sinking, etc,etc,...

Answer 6

Yes ofcourse
I agree with you

Answer 7

3th law ??? No it's not stupid