Acceleration Due To Gravity: Why Is It the Same for All Bodies?

[coverme]

Er... F=ma even in your second statement. It is directly proportional even when F changes. If not, basic Newtonian physics that we ask in undergraduate physics classes will fail. Would you think no one would have noticed this before?

When Put at a location r1 from M. The force that m1 experience is F(r1). If you let go of that mass, it will start accelerating with a1, which is equal to F(r1)/m1. However, when it has moved to another location r2, if you instantaneously measure its acceleration there, you will see that a2 = F(r2)/m. And so on.

This is basic physics. You were applying the wrong thing to the wrong situation.

Zz.

if same force applied to the two body ,the non hevier would accelerate more and heavier would accelerate less.
i come in serious conclusion that the daily life physical force,there is defined force first and acceleration as its effect defined at second
but in gravity , its the acceleration due to gravity is defined first(which is non concerned to amount of mass of affected body) and only force experienced is defined at second.these are the differences between 2nd law and gravity
I am rigid in my theory

 

[ZapperZ]

if same force applied to the two body ,the non hevier would accelerate more and heavier would accelerate less.
i come in serious conclusion that the daily life physical force,there is defined force first and acceleration as its effect defined at second
but in gravity , its the acceleration due to gravity is defined first(which is non concerned to amount of mass of affected body) and only force experienced is defined at second.these are the differences between 2nd law and gravity
I am rigid in my theory

The rigidity of your "theory" has nothing to do with its validity. You are welcome to believe in false and faulty understanding. But it is against our https://www.physicsforums.com/showthread.php?t=5374" to perpetuate those false ideas on here, and nothing you have said here has contradicted either the gravitational laws or the Newton's laws.

Zz.

 

[Cantab Morgan]

I meant that the gravity is not same kind of force as physical forces in daily life.(not the Newtonian concern) Gravity interaction is of different nature than the physical forces

I don't think you're going to get any traction behind that idea. Have another look at DH's posts. Sorry coverme, but you are either flat wrong, or you are expressing yourself so poorly that it's not making any sense.

Is the electrostatic force different from the "physical forces in daily life"? mikelepore had some good thoughts about this. If I have a bunch of charged particles, every single one of them is pulled (or pushed) by the electrostatic force. If I have a bunch of massive particles, every single one of them is pulled by the gravitational force.

if same force applied to the two body ,the non hevier would accelerate more and heavier would accelerate less.

True.

i come in serious conclusion that the daily life physical force,there is defined force first and acceleration as its effect defined at second
but in gravity , its the acceleration due to gravity is defined first(which is non concerned to amount of mass of affected body) and only force experienced is defined at second.these are the differences between 2nd law and gravity

Unintelligible. Or maybe crackpot. I can't tell.

I am rigid in my theory

Well, I'm happy for you. But I'll stick with Newton.

 

[TurtleMeister]

I'm not sure, but I think one of the things that coverme is trying to convey is the fact that gravity accelerates all particles equally at the same time. If you're accelerating or free-falling due to gravity, you do not feel it because gravity accelerates all particles of your body equally, even the tiniest (disregarding tidal forces). So there are no pressure points for you to feel. If you are accelerated by say a rocket ship then you feel the pressure because it is applied to your feet and it is transferred through your body. But I strongly disagree with coverme's concept of gravity as having a special case in Newtons laws of motion. This is flat wrong, as DHs post demonstrates.

 

[AUMathTutor]

I don't know about you guys, but I can certainly tell the difference between being at a relatively low acceleration and being in free fall.

The equal acceleration of objects falling near Earth's surface is an approximation. Physicists like to think that functions are equal to the first (and if you want to be technical, the second as well) term in the Taylor series expansion.

 

[TurtleMeister]

I don't know about you guys, but I can certainly tell the difference between being at a relatively low acceleration and being in free fall.

Did someone imply that you could not tell the difference? I must have missed that. Can you provide quotes.

 

[Nabeshin]

The equal acceleration of objects falling near Earth's surface is an approximation.

Perhaps the assertion that 'g' is constant is an approximation (very good for every day life), but I don't think the fact that all objects fall with equal acceleration is (even if this number is not g). The fact is, gravitational force is directly proportional to mass, and so is acceleration, so they will always cancel each other out. There is no approximation in that.

Even if my bowling ball and feather are 100km above the Earth's surface, they will experience equal accelerations (no air resistance, of course).

 

[coverme]

I'm not sure, but I think one of the things that coverme is trying to convey is the fact that gravity accelerates all particles equally at the same time. If you're accelerating or free-falling due to gravity, you do not feel it because gravity accelerates all particles of your body equally, even the tiniest (disregarding tidal forces). So there are no pressure points for you to feel. If you are accelerated by say a rocket ship then you feel the pressure because it is applied to your feet and it is transferred through your body. But I strongly disagree with coverme's concept of gravity as having a special case in Newtons laws of motion. This is flat wrong, as DHs post demonstrates.

your feet attached to spacecraft ,you may feel pressure point at your feet but do you feel you are devoted to gravity there that you judge the direction as in you are in earth.

 

[coverme]

The rigidity of your "theory" has nothing to do with its validity. You are welcome to believe in false and faulty understanding. But it is against our https://www.physicsforums.com/showthread.php?t=5374" to perpetuate those false ideas on here, and nothing you have said here has contradicted either the gravitational laws or the Newton's laws.

Zz.

I know its a way of understanding and no one is perfect.Even the Newton an eeinstein while formulating their laws may have a lot of confusion in themselves,but they try to gave approximation
Some thing we have to generate from ourselves also then how can science progress.

 

[ZapperZ]

I know its a way of understanding and no one is perfect.Even the Newton an eeinstein while formulating their laws may have a lot of confusion in themselves,but they try to gave approximation
Some thing we have to generate from ourselves also then how can science progress.

But what does what you have done here have anything to do with progress? Progress can't be made when it's based on ignorance. And your comment about Einstein and Newton is nothing more than an amusing noise.

I think this thread has outlived its purpose. We are not obliged to correct your misunderstanding if you're not willing to learn.

Zz.