Some questions about Physics..

[Smokinjoe9]

I do not want to start any sort of argument, I am delving deeper into physical science and would like to talk about a few things...

 

do not totally disagree with Newton's laws of motion, but I do have some questions...

 

Whenever one body exerts force upon a second body, the second body exerts an equal and opposite force upon the first body.

Ok, 2 bodies no force, they sit there..(trivial I know), when force is exerted by one body it is applied to the second body, the mass of the second does not cause the second body to exert force?, it is just mass?

 

One example of this law is if you push against a door with a certain force, the door is also pushing with the same force against you.

 

This is my problem(I am trying to get past it), Pushing on the door requires you to use a certain amount of energy(that you don't get back), It is transfered to the door?, it pushes back? It has mass, but it does not push back, as I see it as the bigger the 2nd object the more force that has to be exerted and yes it seems like the door is pushing back....

But, what is first cause then, what pushed first...Isn't the amount of force used to push the door = to the amount of force it takes to move it?

 

I am just getting started, please don't freak at me, for me this is the place to ask these questions...It may seem dumb to you, and if you would like I could skip it on this board, but I know there is an argument here somewhere....Joe.

[Smokinjoe9]

Yes, this another question that may seem rediculous to you but not to me.

 

If you jump off a ladder, the force of gravity will pull you to the Earth according to F = m*g, where m is your mass and g is the acceleration due to gravity.

 

But that same force is working in an opposite direction on the Earth, pulling it toward you according to F = M*G, where M is the mass of the Earth and G is its acceleration.

Since the mass of the Earth is so much greater than your mass, its movement is extremely small.

 

So I have have a gravitational pull because I have mass? In space I would attract objects(hypothetically) due to my mass, or must I be spinning and have mass?

[UncleAl]

Physics, 5th edition, Volumes 1 and 2, Halliday, Resnick, Krane, 2002.

 

Lots of pictures. Read it. If you want it straight from the lion's paw,

 

Newton, Isaac (1687). The Principia: Mathematical Principles of Natural Philosophy Trans. I. Bernard Cohen and Anne Whitman, with the assistance of Julia Budenz (University of California Press: Berkeley, 1999)

[Smokinjoe9]

Physics, 5th edition, Volumes 1 and 2, Halliday, Resnick, Krane, 2002.

 

Lots of pictures. Read it.

 

Maybe, I could just look at the pictures?

[Smokinjoe9]

I would just like to understand it better, or even get it for that matter. References to actual experiments would be cool I guess...I guess I could buy the book you suggest, just thought some imput from here would be fun..

[Smokinjoe9]

So I have have a gravitational pull because I have mass? In space I would attract objects(hypothetically) due to my mass, or must I be spinning and have mass?

 

Maybe just an answer to this question?

[Smokinjoe9]

???? one reply?

[Smokinjoe9]

Pendulum

 

If you swing a weight on a string, it will go back and forth in regular periodic motion. Once it got started, such a pendulum would move back-and-forth forever if it was not for internal friction in the string and air resistance.

 

and gravity? or is that a given?

[Smokinjoe9]

One example of this law is if you push against a door with a certain force, the door is also pushing with the same force against you.

 

This is my problem(I am trying to get past it), Pushing on the door requires you to use a certain amount of energy(that you don't get back), It is transfered to the door?, it pushes back? It has mass, but it does not push back, as I see it as the bigger the 2nd object the more force that has to be exerted and yes it seems like the door is pushing back....

But, what is first cause then, what pushed first...Isn't the amount of force used to push the door = to the amount of force it takes to move it?

 

Newton's Laws of Inertia state that force is required to change the motion of matter. The force require to accelerate an object is proportionate to the mass of the object.

 

So, the object being forced is not pushing back? It just takes enough force to overcome the mass/weight of object 2..

[Mac]

Maybe just an answer to this question?

 

No spinning required. My only other comment would be that you should also give due consideration to "Push Gravity", not simply "Mass Attraction" or "Curved Time-Space".

[Mac]

Pendulum

 

If you swing a weight on a string, it will go back and forth in regular periodic motion. Once it got started, such a pendulum would move back-and-forth forever if it was not for internal friction in the string and air resistance.

 

and gravity? or is that a given?

 

In a perfect system gravity would keep the pendulm in motion perpetually.

[Smokinjoe9]

No spinning required. My only other comment would be that you should also give due consideration to "Push Gravity", not simply "Mass Attraction" or "Curved Time-Space".

 

 

Ok, I'm getting there, I first have to get past..An object has gravity because it has mass????? I'm working on it, I have not done the experiments myself so, I have to assume this is correct...hypothetically, 2 rocks places side by side in space do not attract they just sit there, correct?

I mean if I set them side by side(sitting still) in space they wil no come together, right?

[Smokinjoe9]

"Physicist Albert Einstein examined gravity in his study of the Theory of Relativity. He noticed that if you are in an elevator that was going up, you felt heavier due to the acceleration of the elevator's motion.

 

Einstein concluded that since the force from acceleration had the same effect as the force caused by gravity, there must be some mathematical relationship between the two. In fact, he said that gravity was actually caused by acceleration.

 

That idea is not too clear, since when the elevator is accelerating upward, it is directly pushing on you. On the other hand, gravity is a force that acts at a distance through some force field or perhaps unknown means. Perhaps gravity is similar to acceleration, but not caused but it."

 

Confusion, and not just for me...

 

 

Curvature of space

 

"Later Einstein postulated that the presence of matter distorts the space around it.

 

This can be explained by picturing space as a grid of lines. Without matter, space would be a perfect grid of parallel lines. An object would move in a straight line through space.

 

The presence of another mass of matter would distort the lines, drawing some toward it. Thus a moving object would no longer travel in a straight line. Instead, it would curve toward the other object, appearing to be attracted to it.

 

This is a pretty abstract explanation, but Einstein demonstrated it with highly complex mathematical equations. Many scientists accept this concept of the curvature of space."

 

The math works for this particular theory..

I am not convinced, for many reasons..They may stem from a lack of knowledge, we'll see..Oh this also must mean the objects(astroids etc..) moving through space also curve space, right?

Planets, sitting in space "curve" the space around them and that is why they "appear" to attract objects?

What about the continous growth of space?

While space expands do the galaxies(masses) move with it/because of it?

If no then space expands from everywhere, and if so then expands from around the masses bent by them and not bent where they are not?

Hold on I'm thinking...As you can tell there is alot I do not understand, but do not let that stop you from contradicting me....

[TeleMad]

No spinning required. My only other comment would be that you should also give due consideration to "Push Gravity", not simply "Mass Attraction" or "Curved Time-Space".

 

My comment is ... don't listen to Mac. If you are learning physics, learn normal physics. In standard physics texts - such as the college physics text sitting next to me now - you find both "mass attraction" (Newtonian) and "curved spacetime" (Einsteinian) descriptions of gravity; you won't find "push gravity" discussed.

 

Don't get sidetracked with hypothetical mumbo jumbo: stick to physics proper. Doing as Mac suggests will only confuse you more.

[Smokinjoe9]

My comment is ... don't listen to Mac. If you are learning physics, learn normal physics. In standard physics texts - such as the one sitting next to me now - you find both "mass attraction" (Newtonian) and "curved spacetime" (Einsteinian) descriptions of gravity; you won't find "push gravity" discussed.

 

Don't get sidetracked with hypothetical mumbo jumbo: stick to physics proper. Doing as Mac suggests will only confuse you more.

 

I am glad to get any responses, and I am studing Newton and Einstein..That is where I have the trouble. I cannot find anything that says curved spacetime is proven true....If it can be done, I would like to have some of my questions answered...

[Smokinjoe9]

In a perfect system gravity would keep the pendulm in motion perpetually.

Not if it pulls straight down..

[Smokinjoe9]

2 rocks places side by side in space do not attract they just sit there, correct?

I mean if I set them side by side(sitting still) in space they will not come together, right?

 

Like this question, it is simple, and I know you guys can answer it please do...