How stuff works--4

[ws23rt]

Since there are way too many chargers laying around rusting away I thought a couple may be put to good use.

An imaginary experiment for thinking about an old law about gravity.

So two chargers are hanging suspended lets say 100ft up.  The difference between the two is the drive train is missing from one of them.

We know that when they are cut loose they will strike the ground at the same time.

The question is why?  The one that has the engine and trans is hundreds of pounds heaver than the other.  The pull of gravity pulls harder on it by that amount.

BTW if one of them was a daytona it would hit the ground first.  So the air is not part of this. 

[XH29N0G]

Think I need a whiskey to help me think about this 

[ws23rt]

It may help---

[XH29N0G]

It may help---

Thanks for posting this.  It is not something I  ever thought about, but I think I learned something.

I'll stick around sipping to see if it is right or wrong. 

[Ram07]

Isn't that like asking what's gonna hit the ground first....a ton of feathers, or a tone of bricks?

[ws23rt]

A ton of feathers and a ton of bricks weigh the same.  Ignoring the influence of air they are the same thing.

In this case the weights are different but they still hit the ground at the same time.

[Ram07]

once in free fall...isn't everything the same?

[ws23rt]

once in free fall...isn't everything the same?

The question is why do different weights fall at the same rate?

[Ram07]

wouldn't it depend on what height they were falling from?

[ws23rt]

No

[Ram07]

 ...dammit....I almost remember this....guess using the google machine is cheating, right?

[XH29N0G]

I find all this talk about dropping chargers a little disturbing.  Why not leave the chargers out of it and save em for  .  Couldn't we instead drop a ricer and dump truck?   

[ws23rt]

Hey---just trying to include chargers that are rusting away.
BTW all the wrinkles can be fixed. And in our minds it is cheap.

[Fred]

once in free fall...isn't everything the same?

The question is why do different weights fall at the same rate?

I'm guessing there's a severe down draught.   

[Chargerguy74]

The acceleration due to gravity is a constant 9.81 meters per second per second. So lets say in a void, excluding all drag, wind resistance etc. both cars would accelerate towards the earth at the same rate from a speed (or velocity if you will, since we have direction) of zero at the time of release and would impact the earth at the same time. The difference in mass of the objects will have no bearing on the acceleration imparted by the Earth's gravity. Obviously the car with the greater mass will have more kinetic energy at impact and hit the earth with more force since force is mass x acceleration.

[XH29N0G]

I think ws23RT was asking why weight/mass causes no change with acceleration due to gravity, but it sure has a lot to do with acceleration when we use the wheels of our cars.

I'm also waiting for the answer.  I have an idea that I want to check, but I don't want to spoil the fun it if it is right.

[ws23rt]

You have described what is taking place in the example and it is indeed true.
Both cars will accelerate toward the ground at the same rate.
It is true that the difference in the mass of the objects will not make a difference and that is why they hit the ground at the same time.
The question is why do they both accelerate at the same rate---

As XH pointed out---When we accelerate our cars there is a real difference in the amount of energy required to move a heavy car vs a light car

[Chargerguy74]

So basically, you're asking why gravity behaves the way it does?

[ws23rt]

No ---This is just an exercise in how the world we live in works.  We all know the answer because we live with these forces our whole lives.  ( I should say our instincts feel the answer.)  The language of physics is just a way to talk about stuff we know already.

Not unlike observing bad behavior  ---We all know it when we see it but a term or explanation just just describes what we already know

It may seem to be a kind of trick question but it is not.

[Chargerguy74]

Acceleration is just the change in velocity per given time. It really has zero to do with the mass of an object, as it is only the rate of change of velocity. Acceleration due to gravity is a constant 9.81 m/s/s or 32.2 ft/s/s. No where in those units do you see lbs, kg, etc as mass has no influence on the acceleration by gravity. Why doesn't it? Why would it? The gravitational force of attraction between the mass of an object and the mass of the earth is like I said F=ma. So the force of attraction will be greater between the Earth and the car with greater mass, but the acceleration is still a constant (the earth's mass is constant) as it's only the rate of change of velocity. I know this still isn't a satisfying answer, and I don't think I can give you one.

[Chargerguy74]

I don't see it as a trick question. I've spent enough time with Applied Mechanics and Newton's laws of motion to see how these things work. "Why" is a totally different animal. Why is there a force of attraction between objects?

[ws23rt]

You are correct in your description of what is happening.

And the reason the acceleration rate is the same is?

[ws23rt]

Your question about ---why is there a force of attraction between objects?----

That is one that I have wondered about since I first fell down

It is IMHO the ---at the same time---- most predictable and least understood of the forces we live with.
Even magnetism is better understood.

[Chargerguy74]

You didn't really expect to get an answer here for why gravity works the way it does did you? I mean, is it even fully understood today among physicists? I was mistaken when I read the title of the thread "How stuff works" it's more of a "why things work the way they do". And for that, I do not have an answer 

[ws23rt]

You didn't really expect to get an answer here for why gravity works the way it does did you? I mean, is it even fully understood today among physicists? I was mistaken when I read the title of the thread "How stuff works" it's more of a "why things work the way they do". And for that, I do not have an answer.

No not at all.  That is not what I meant when I went on about how gravity is little understood.  It was a side comment about gravity.


Ok  here is a hint about the answer to the question---  The heaver car will not accelerate faster because it is heaver---

[Chargerguy74]

I'm not sure what you're getting at when you say the air is not a part of this. In the real world the Daytona would more than likely hit first because of the nose cone being more aerodynamic. This is why I said "So lets say in a void, excluding all drag, wind resistance etc. both cars would accelerate towards the earth at the same rate from a speed (or velocity if you will, since we have direction) of zero at the time of release and would impact the earth at the same time."

But I think what you're getting at is the Daytona hits first because they are both suspended from the same height, true?
Are they hanging from two chains 100 feet above the earth, both attached to the same point on each car, making the Daytona closer to the earth by it's nose cone? Or do they both have 100 feet between their lowest hanging points and the earth?

Sorry I didn't think you were looking for a real answer to a question I obviously missed in the first post.

[Fred]

You didn't really expect to get an answer here for why gravity works the way it does did you? I mean, is it even fully understood today among physicists? I was mistaken when I read the title of the thread "How stuff works" it's more of a "why things work the way they do". And for that, I do not have an answer.

No not at all.  That is not what I meant when I went on about how gravity is little understood.  It was a side comment about gravity.


Ok  here is a hint about the answer to the question---  The heaver car will not accelerate faster because it is heaver---

I have it on good authority that less than a significant fraction of 1% of everything is only known (understood by) to man.

[Chargerguy74]

You didn't really expect to get an answer here for why gravity works the way it does did you? I mean, is it even fully understood today among physicists? I was mistaken when I read the title of the thread "How stuff works" it's more of a "why things work the way they do". And for that, I do not have an answer.

No not at all.  That is not what I meant when I went on about how gravity is little understood.  It was a side comment about gravity.


Ok  here is a hint about the answer to the question---  The heaver car will not accelerate faster because it is heaver---

I have it on good authority that less than a significant fraction of 1% of everything is only known (understood by) to man.

I agree

[ws23rt]

I suppose we need to go back to the first post.

The reason I said air is not part of this is this is an example of acceleration.   If one were to drop a balloon and a basket ball the balloon would of course take much longer.  If there were no air they would hit the ground at the same time.

The same goes for the daytona--It would cut through the air better and hit the ground first.

My intent from the beginning was for this to not be a trick question.

[Chargerguy74]

  I'm done

[ws23rt]

You didn't really expect to get an answer here for why gravity works the way it does did you? I mean, is it even fully understood today among physicists? I was mistaken when I read the title of the thread "How stuff works" it's more of a "why things work the way they do". And for that, I do not have an answer.

No not at all.  That is not what I meant when I went on about how gravity is little understood.  It was a side comment about gravity.


Ok  here is a hint about the answer to the question---  The heaver car will not accelerate faster because it is heaver---

I have it on good authority that less than a significant fraction of 1% of everything is only known (understood by) to man.

You never know Fred who you are talking to   I may be the one person that knows the tiny fraction of a percent of something.  

[Fred]

You didn't really expect to get an answer here for why gravity works the way it does did you? I mean, is it even fully understood today among physicists? I was mistaken when I read the title of the thread "How stuff works" it's more of a "why things work the way they do". And for that, I do not have an answer.

No not at all.  That is not what I meant when I went on about how gravity is little understood.  It was a side comment about gravity.


Ok  here is a hint about the answer to the question---  The heaver car will not accelerate faster because it is heaver---

I have it on good authority that less than a significant fraction of 1% of everything is only known (understood by) to man.

You never know Fred who you are talking to   I may be the one person that knows the tiny fraction of a percent of something.  

Well I was willing to allow 2% but apparently that's utterly absurd.   

[ws23rt]

You didn't really expect to get an answer here for why gravity works the way it does did you? I mean, is it even fully understood today among physicists? I was mistaken when I read the title of the thread "How stuff works" it's more of a "why things work the way they do". And for that, I do not have an answer.

No not at all.  That is not what I meant when I went on about how gravity is little understood.  It was a side comment about gravity.


Ok  here is a hint about the answer to the question---  The heaver car will not accelerate faster because it is heaver---

I have it on good authority that less than a significant fraction of 1% of everything is only known (understood by) to man.

You never know Fred who you are talking to   I may be the one person that knows the tiny fraction of a percent of something.  

Well I was willing to allow 2% but apparently that's utterly absurd.   

I feel complemented but any one can make a mistake in judjment

[Fred]

You didn't really expect to get an answer here for why gravity works the way it does did you? I mean, is it even fully understood today among physicists? I was mistaken when I read the title of the thread "How stuff works" it's more of a "why things work the way they do". And for that, I do not have an answer.

No not at all.  That is not what I meant when I went on about how gravity is little understood.  It was a side comment about gravity.


Ok  here is a hint about the answer to the question---  The heaver car will not accelerate faster because it is heaver---

I have it on good authority that less than a significant fraction of 1% of everything is only known (understood by) to man.

You never know Fred who you are talking to   I may be the one person that knows the tiny fraction of a percent of something.  

Well I was willing to allow 2% but apparently that's utterly absurd.   

I feel complemented but any one can make a mistake in judjment

You are sorely mistaken..........there is one among us that makes no mistakes. 

[ws23rt]

Is he still hear?

[Fred]

Is he still hear?

[green69rt]

I think the answer to this riddle is that the objects do not actually fall at the same rate but the difference is so infinitesimal that we can't measure it.

The basic science is Newton laws of Gravity.  One says that two bodies will mutually attract each other with a force proportional to the sum of their mass and proportional to the inverse of the square of the distance separating them.   Now all that said, then Einstein shot a hole in the law when he proposed the laws of general relativity.   But Newton's law works so good in the world we normally operate in that it's still commonly used.

So take the car falling, what's actually happening is the earth and the car are falling toward each other, but the earth has such a huge mass that its movement would be impossible to measure, the car does all the moving.  The heavier car and the earth are actually falling toward each other faster, but since the earth is still so much bigger than the car and "proportional to the sum of the mass" rule applies -  we can't tell the difference and we say both cars fall at the same rate.

I had to dredge up old high school physics but I think I'm close.

[XH29N0G]

I'll state my guess because last time I was wrong in the end.

I'll also l leave a bit for Fred below.  

So when we try to get two cars to accelerate on a flat surface and they have exactly the same traction, power, torque etc... but different mass, the lighter one accelerates quicker.  This is because the force divided by the mass equals the acceleration.  The first thing I thought of with the falling cars was the mass was only pulling down (force of gravity = mass * gravitational acceleration), but then I thought this would make the force greater on the heavier car - which is puzzling. So then I thought what is holding it back (stopping it from accelerating)?

I then started wondering whether it was the same thing that made a difference for the cars accelerating on the road, which brought me to momentum, (maybe inertia for the the chargers hanging in the air). 

Here is what I think. Force of gravity (mass * acceleration) fights against momentum or inertia (mass times velocity). This means that the force of gravity and momentum (inertia) both scale with mass in the same way and the acceleration and velocity of both cars end up being the same.  I'm not a physicist so I probably messed up the language, but that is my guess.

PS..Hey Fred,

When I first met my (now) wife, she handed me a book with some Alexander Pope in it and asked me to read it.  The first part is below.  It doesn't really deal with the 1%, but it describes part of our plight partly knowing people.  (There is more to the essay (on man) but I found it fun to read.  My favorite part of the story is when a bunch of aliens abduct the smartest guy on earth. - I never thought about people in the 1800's thinking about aliens.)

Know then thyself, presume not God to scan
The proper study of Mankind is Man.
Placed on this isthmus of a middle state,
A Being darkly wise, and rudely great:
With too much knowledge for the Sceptic side,
With too much weakness for the Stoic's pride,
He hangs between; in doubt to act, or rest;
In doubt to deem himself a God, or Beast;
In doubt his mind or body to prefer;
Born but to die, and reas'ning but to err;
Alike in ignorance, his reason such,
Whether he thinks too little, or too much;
Chaos of Thought and Passion, all confus'd;
Still by himself, abus'd or disabus'd;
Created half to rise and half to fall;
Great Lord of all things, yet a prey to all,
Sole judge of truth, in endless error hurl'd;
The glory, jest and riddle of the world.

[b5blue]

Good stuff! 
  The distortion of Time/Space by the mass of our planet appears to pull other mass to it. The lesser mass is actually moving along this distortion of Time/Space. Think back to the Apollo 15 mission to our moon, a hammer and a feather were dropped and both fell at the same rate. (No air to effect the fall rate.)
http://nssdc.gsfc.nasa.gov/planetary/lunar/apollo_15_feather_drop.html 
  The warp of Time/Space is fascinating, while very slight even Time is effected to a verifiable rate.
http://physicsworld.com/cws/article/news/2010/feb/17/gravitys-effect-on-time-confirmed
   Weight or total mass of the Chargers will not (No pun intended.) matter. Every atom, even every proton and neutron in the atom that combined make up the Chargers, in in this warp are effected exactly the same. This only leaves the density of the atmosphere to effect the fall. The only difference in the fall rate would be the aerodynamic difference from the extra parts ether increasing or decreasing drag as the Chargers moved when dropped.
    At least that is my answer to the posed question......    

[ws23rt]

I'll state my guess because last time I was wrong in the end.

I'll also l leave a bit for Fred below.  

So when we try to get two cars to accelerate on a flat surface and they have exactly the same traction, power, torque etc... but different mass, the lighter one accelerates quicker.  This is because the force divided by the mass equals the acceleration.  The first thing I thought of with the falling cars was the mass was only pulling down (force of gravity = mass * gravitational acceleration), but then I thought this would make the force greater on the heavier car - which is puzzling. So then I thought what is holding it back (stopping it from accelerating)?

I then started wondering whether it was the same thing that made a difference for the cars accelerating on the road, which brought me to momentum, (maybe inertia for the the chargers hanging in the air).  

Here is what I think. Force of gravity (mass * acceleration) fights against momentum or inertia (mass times velocity). This means that the force of gravity and momentum (inertia) both scale with mass in the same way and the acceleration and velocity of both cars end up being the same.  I'm not a physicist so I probably messed up the language, but that is my guess.

   Inertia is what holds the heaver car back (from accelerating faster). It has a greater mass therefore a greater resistance to acceleration.

Inertia of motion is the same thing as inertia of rest.  A body in motion will remain in motion until a force acts against it. The same for a body at rest.

As the cars are hanging they are under the influence of gravity force and acceleration but the cables hold them back canceling acceleration to zero.

When the cars are released acceleration begins for both cars and the earth. The earth has more mass therefore greater inertia of rest but will move some also.  Whether the earth moves toward the cars or the cars move toward the earth depends on the point of view.  The distance between them decreases at the constant rate.

BTW  A car on the ground accelerating going east pushes against the ground and will increase the speed at which the earth turns.
On the return trip home (west) it will slow the earth back down.

 Now lets all go make the world go around with our cars

[XH29N0G]

BTW  A car on the ground accelerating going east pushes against the ground and will increase the speed at which the earth turns.
On the return trip home (west) it will slow the earth back down.

I wonder if I could use that as an excuse for being late on my return from driving the car ..."Honey, I headed east on the way out and......"

Actually, I was in a room last Spring when someone said that they could see changes in the Earth's rate of rotation related to storminess in northern hemisphere vs southern hemisphere winter.  I think this was with satellites.  It really made me think about what we know and can do.  I assume it is figure skater/ballerina type effect?

I have absolutely no intuition about warping time and space.   

[ws23rt]

BTW  A car on the ground accelerating going east pushes against the ground and will increase the speed at which the earth turns.
On the return trip home (west) it will slow the earth back down.

I wonder if I could use that as an excuse for being late on my return from driving the car ..."Honey, I headed east on the way out and......"

Actually, I was in a room last Spring when someone said that they could see changes in the Earth's rate of rotation related to storminess in northern hemisphere vs southern hemisphere winter.  I think this was with satellites.  It really made me think about what we know and can do.  I assume it is figure skater/ballerina type effect?

I have absolutely no intuition about warping time and space.[/quote]


I have the same lack of intuition about warping time and space.  I see the theory's about this as an explanation.  Things must be this way in order for everything to fit as we see them.
Our minds are not engineered to grasp some things.  
Infinity is a good example of something we can talk about but not grasp fully.

Two lines---- line -A-starts at a point and goes to infinity.  Another line-B-goes both ways to infinity.
Line A is 1/2 as long as line B but has no center.   On line B every point is the center.  And they are both the same length (infinite)

[Fred]

PS..Hey Fred,

When I first met my (now) wife, she handed me a book with some Alexander Pope in it and asked me to read it.  The first part is below.  It doesn't really deal with the 1%, but it describes part of our plight partly knowing people.  (There is more to the essay (on man) but I found it fun to read.  My favorite part of the story is when a bunch of aliens abduct the smartest guy on earth. - I never thought about people in the 1800's thinking about aliens.)

Know then thyself, presume not God to scan
The proper study of Mankind is Man.
Placed on this isthmus of a middle state,
A Being darkly wise, and rudely great:
With too much knowledge for the Sceptic side,
With too much weakness for the Stoic's pride,
He hangs between; in doubt to act, or rest;
In doubt to deem himself a God, or Beast;
In doubt his mind or body to prefer;
Born but to die, and reas'ning but to err;
Alike in ignorance, his reason such,
Whether he thinks too little, or too much;
Chaos of Thought and Passion, all confus'd;
Still by himself, abus'd or disabus'd;
Created half to rise and half to fall;
Great Lord of all things, yet a prey to all,
Sole judge of truth, in endless error hurl'd;
The glory, jest and riddle of the world.

Thanks a bunch for sharing that beautiful piece of wisdom XH29N0G. It's 10.45 am here and I'm just about to have a coffee outside on the patio. And while I'm enjoying what mother nature is offering up today, I will ponder on how best to instruct the planets in what orbs to run.