The connection between Anti-Science and Anti-Education views.

@livinglava,

Quote:

I'm not going by intuition. Look up the force of gravity for different planets. Mars has around 1/3 Earth's gravity. Venus is also less but not as low as Mars. Jupiter and Saturn have greater gravity. The gravity is related to the mass.

I may have interpreted Newton's formula wrong in assuming that the inclusion of two mass numbers in the numerator accounts for different acceleration rates in different gravitational fields, but now I am looking for an explanation for different gravity on different planets. You just proved mathematically that the explanation isn't in Newton's equation, so where is it?

Newton's laws work the same on any planet.

F = ma (on any planet)
F = GMm/(r^2) (on any planet).

From there you can do the math. On any planet

a = GM/(r^2)

This means the mass of a dropped object has zero effect on its acceleration. This is true on any planet. Of course, the math says that objects will fall at different rates on different planets depending on the mass of the planet and the radius of the planet.

2 Replies

@maxdancona,

maxdancona wrote:

Quote:
I'm not going by intuition. Look up the force of gravity for different planets. Mars has around 1/3 Earth's gravity. Venus is also less but not as low as Mars. Jupiter and Saturn have greater gravity. The gravity is related to the mass.

I may have interpreted Newton's formula wrong in assuming that the inclusion of two mass numbers in the numerator accounts for different acceleration rates in different gravitational fields, but now I am looking for an explanation for different gravity on different planets. You just proved mathematically that the explanation isn't in Newton's equation, so where is it?

Newton's laws work the same on any planet.

F = ma (on any planet)
F = GMm/(r^2) (on any planet).

From there you can do the math. On any planet

a = GM/(r^2)

This means the mass of a dropped object has zero effect on its acceleration. This is true on any planet. An object will fall at different rates on different planets depending on the mass of the planet and the radius of the planet.

What you just said amounts to saying that a digital camera that works on Earth will also take pictures on Mars.

You didn't explain the differences in gravity by saying the gravity equations work on different planets.

1 Reply

@maxdancona,

I want to repeat the story because I think it is fascinating. Isaac Newton is often considered the father of modern Physics, and it was the ability of his mathematical model to describe Nature both on Earth and in "the heavens" that changed the world.

We take it for granted now, but it was Amazing to people of Newton's day. It is astonishing that you can have one set of mathematical equations that rule the behavior of objects whether they were on Earth or in Space or anywhere in the Universe.

There was a fascinating set of letters between Newton and Hooke (a great contemporary Physicist) where they work out the motion of an object in a "centripedal force". Newton was able to apply his mathematical laws to all of the planets. Which is amazing... but still he was solving a problem where he already knew the correct answer.

Newton's mathematics reigned triumphant when it correctly predicted the appearance and orbits of comets. In this case they were used to make predictions before the result was known that could then be confirmed by observation.

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@livinglava,

Quote:

You didn't explain the differences in gravity by saying the gravity equations work on different planets.

Code:



A = GM/(r^2)

This explains the different gravitational accelerations on different planets. I even showed how this is derived from Newton's laws.

1 Reply

@maxdancona,

maxdancona wrote:

Quote:
You didn't explain the differences in gravity by saying the gravity equations work on different planets.

Code:A = GM/(r^2)

This explains the different gravitational accelerations on different planets. I even showed how this is derived from Newton's laws.

What you mean to say is that the same equation can be used on different planets.

That is like saying the same camera takes pictures the same way on Mars as it does on Earth.

You are not explaining why gravity is different on different planets, i.e. why the rate of acceleration is different.

If you were teaching kids in an elementary school class how gravity works, what answer would you give them as to why things fall faster on Earth than Mars and faster on Jupiter than Earth?

Would you just teach the math and tell them that's all science can do?

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@livinglava,

The answer is right there Lava. I don't know how to spell it out for you. You take the Mass of Jupiter and the radius of Jupiter. You plug it into the equation and you get the answer.

Why is the acceleration gravity on Jupiter different from that on Earth? Because the mass and radius of Jupiter are different than the mass and radius of Earth.

I don't know how to make this any simpler.

1 Reply

I have never taught Physics to elementary school students. Elementary school science is a little weird... when I was taking Education classes I learned a little bit about that age, but that wasn't my specialty.

It is impossible to teach real Physics to students who don't understand algebra. Physics is about making predictions that can be tested by experiment.

When you teach Physics, you aren't just giving kids the answers. You are giving them the ability to derive the answers for themselves. A good teacher doesn't just tell kids what to believe. A good teacher will give their students the skills to check for themselves and, in fact, insist that they do so. When I was a student, there were many an exam question that started "Prove that.....". I didn't just have to give the correct answer, I had to explain how I knew it was correct.

You really can't confirm anything in Physics without a decent knowledge of at least algebra. I had trouble teaching non-honors high school students. Since they didn't know calculus they couldn't check the equations I was giving them for themselves. As a teacher I felt bad about that.

The students who understand calculus before taking Physics (or were taking the two classes simultaneously) have a much more valuable experience.

In a serious University course, you must know calculus before you start a real study of Physics.

1 Reply

@maxdancona,

maxdancona wrote:

The answer is right there Lava. I don't know how to spell it out for you. You take the Mass of Jupiter and the radius of Jupiter. You plug it into the equation and you get the answer.

Why is the acceleration gravity on Jupiter different from that on Earth? Because the mass and radius of Jupiter are different than the mass and radius of Earth.

I don't know how to make this any simpler.

That's exactly why I said the slightly-greater mass of the second cannonball would cause slightly greater acceleration than the lighter one, but then you insisted that the force would double because the 2x factor of the cannonball mass being double would double the overall result.

Actually, I think the problem is that the equation should involve adding the two masses instead of multiplying them, so doubling the small mass of the cannonball would not change the sum mass of the planet plus cannonball in calculating the force for the heavier cannonball. It would be greater, because the sum in the numerator would be slightly greater, but the difference would be so insignificant as a proportion of the total mass that includes the entire planet.

But maybe my logic is still wrong. If so, explain again how the acceleration remains the same despite the doubling of cannonball mass.

1 Reply

@livinglava,

This is an experiment you can do easily right now at home.

Get an object with a small mass (say a fork) in one hand. Get an object with a large mass (say a gallon of milk). Hold them out ... and tell me which one of these has a higher force from gravity? One of these will pull down on your hand with a significantly higher force than the other. They will still fall at the same rate.

It is pretty easy to confirm through your own experience. The force of gravity on a 10kg object is twice the force of gravity on a 5Kg object.

Newton's laws are very good at explaining your everyday experience in a mathematical way.

1 Reply

@maxdancona,

maxdancona wrote:

I have never taught Physics to elementary school students. Elementary school science is a little weird... when I was taking Education classes I learned a little bit about that age, but that wasn't my specialty.

It is impossible to teach real Physics to students who don't understand algebra. Physics is about making predictions that can be tested by experiment.

When you teach Physics, you aren't just giving kids the answers. You are giving them the ability to derive the answers for themselves. A good teacher doesn't just tell kids what to believe. A good teacher will give their students the skills to check for themselves and, in fact, insist that they do so. When I was a student, there were many an exam question that started "Prove that.....". I didn't just have to give the correct answer, I had to explain how I knew it was correct.

You really can't confirm anything in Physics without a decent knowledge of at least algebra. I had trouble teaching non-honors high school students. Since they didn't know calculus they couldn't check the equations I was giving them for themselves. As a teacher I felt bad about that.

The students who understand calculus before taking Physics (or were taking the two classes simultaneously) have a much more valuable experience.

In a serious University course, you must know calculus before you start a real study of Physics.

If you can find students of any age/ability level who are attentive and interested enough to learn what you teach them, but they just don't understand math/algebra well, you can and should still teach them about how mechanics works, Newton's laws, thermodynamics, quantum physics, Einstein's theories, etc. so that they can have some idea of why these scientists and aspects of science are important. They may, to your surprise, ask questions that are insightful and/or cause you to think about your own subject material in ways you hadn't before.

Your orientation as a scientist should always be to progress further in your understanding and awareness of how things work. If you don't treat knowledge as something lives, grows, changes, and operates in different ways in different contexts, you're not really honoring the fundamental purpose of science and education.

Obviously I'm not saying that the truth changes, but we are always evolving in the way we understand it and apply what we know and understand.

1 Reply

@livinglava,

If you were attentive and interested enough to learn Physics, the first thing you would do is learn Algebra. If want to learn to read, first you learn the alphabet. If you want to master music, you first learn the scales.

I am learning to play the piano right now. I am learning scale by scale. I am playing real music now... but it will take me a lot of work to where I am an expert pianist (if I ever become one). The process is for me to learn the same 3 major chords, as well as fingering for each scale... step by step.

There are no shortcuts.

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@maxdancona,

maxdancona wrote:

This is an experiment you can do easily right now at home.

Get an object with a small mass (say a fork) in one hand. Get an object with a large mass (say a gallon of milk). Hold them out ... and tell me which one of these has a higher force from gravity? One of these will pull down on your hand with a significantly higher force than the other. They will still fall at the same rate.

It is pretty easy to confirm through your own experience. The force of gravity on a 10kg object is twice the force of gravity on a 5Kg object.

Newton's laws are very good at explaining your everyday experience in a mathematical way.

Read post 662. You contradicted yourself and you are just glossing over it instead of reviewing what you said and where you/we went wrong in our analysis of Newton's equation.

The two masses in the numerator are supposed to be added, not multiplied as we assumed. Multiplying them would double the effect of the cannonball with double the mass, but if you just add them, the difference in mass becomes insignificant as a proportion of the sum of the cannonball and planetary mass together.

So you were right the second time, that the mass of the planet causes the force and thus the acceleration rate to change, but you were wrong the first time, that the heavier cannonball doesn't result in a slightly faster force/acceleration than the lighter cannonball.

1 Reply

I have never been to medical school. I have never taken an anatomy class, or done dissection or talk to a surgeon who knows more than me. But I understand how brain surgery is done... brain surgeons use lots of fancy words... you open the cranium, and the frontal perenilium lobe with a suture stat.

Anyone can do brain surgery, it is just cutting. It isn't like you need education to do cutting. And I have read wikipedia articles,

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@livinglava,

Quote:

The two masses in the numerator are supposed to be added, not multiplied as we assumed. Multiplying them would double the effect of the cannonball with double the mass, but if you just add them, the difference in mass becomes insignificant as a proportion of the sum of the cannonball and planetary mass together.

This is a great example. We can use mathematics to show you that you are wrong. If I were wrong, you could use mathematics to prove it as well. You are wrong (in this case). Of course I could also send you to google to see you were wrong... but this is education, so we should work it out ourselves. And since we have mathematics, we can.

1. Do you agree that a 10kg weight is twice as heavy as a 5kg weight?
2. Do you agree that this means that the force of gravity is twice as strong for a 10kg weight as it is for a 5kg weight?

These questions are setting up definitions... so that we can map our common understanding to the mathematics.

Edit: Adding the next question...
3. Do you agree that the 5kg weight and the 10kg weight will fall at the same rate when dropped from the Tower of Pisa?

1 Reply

@maxdancona,

maxdancona wrote:

Edit: Adding the next question...
3. Do you agree that the 5kg weight and the 10kg weight will fall at the same rate when dropped from the Tower of Pisa?

Empirically, Galileo's experiment only rendered a single sound of the cannonballs simultaneously hitting the ground.

But according to the correct equation with the sum (not the product) of the masses in the numerator, the force increases only slightly as a result of the second cannonball being heavier, and thus there is more gravitational force and faster acceleration (per unit mass from the same height).

We were discussing Gm1m2/d^2 before; when the equation we should have been using was m1+m2/r^2.

Anyway, do you understand why the masses are multiplied in one equation and summed in another? Do you think it is just because the equations are checked against recorded measurements and they fit or do you think there was/is some logical reason the variables are related as a product in one but only a sum in the other?

1 Reply

@livinglava,

There are three yes or no questions. You didn't answer any of them.

If you answer these questions, then we can do the math to see whether your understanding is correct or not.

Please answer the questions--- yes or no.

1 Reply

@maxdancona,

maxdancona wrote:

There are three yes or no questions. You didn't answer any of them.

If you answer these questions, then we can do the math to see whether your understanding is correct or not.

Please answer the questions--- yes or no.

F=MA means that as an object accelerates or decelerates, it exerts/experiences force. It does so because it is no longer remaining in motion due to its inertia.

An object falling is accelerating toward another mass, centripetally according to Newton; and so there is force there according to that definition.

Now you asked me whether a 10kg object exhibits twice as much force as a 5kg object falling due to gravity. According to F=MA, the force would be double for the 10kg object if the acceleration rate is the same.

However, with the formula m1+m2/r^2, the force of gravity is going to be greater if m2 is greater, even if m1 is the mass of the entire planet. That means you're going to have a slightly greater rate of acceleration for the 10kg object than the 5kg object.

Now the problem you have to answer is how to reconcile the two different meanings of 'force' where one only refers to the force any objects exhibits by accelerating; and the other refers to the acceleration rate that gravity imparts in a falling object.

Otherwise put, a 5kg object falling on a planet where gravity accelerates it at 10m/s^2 is exhibiting the same force as a 10kg object falling on a planet where gravitational acceleration is 5m/s^2 because:
1) 5kg x 10m/s^2 = 50kg(m)/s^2
and
2) 10kg x 5m/s^2 = 50kg(m)/s^2

So now you have equal force for both objects according to F=MA, yet you're dealing with only half the gravitational force (acceleration) acting on the 10kg object in comparison with the 5kg one.

So hopefully that's clear and you will cite and explain any mistakes or misconceptions you see that I can't or that I overlooked.

1 Reply

@livinglava,

You answered one of the three questions. And you are writing a lot of words... it boils down to this.

Under Newton's Laws

1) F = ma

2) F = G(Mm)/(r^2)

3) The meaning of the word "force" is the same in both of these equations. There is nothing to reconcile and no contradiction.You can plug in the number for yourself/

So... A 5kg mass will experience a gravitational force of 49N and will accelerate at 9.8 m/s/s.
A 10kg mass will experience a gravitational force of 98N and will accelerate at 9.8 m/s/s.

The two masses have the same acceleration (and hit the ground at the same time). The math all works out correctly (you can check it if you want) and there is no contradiction. If you don't accept this, than plug in the numbers into the equations above and show me where they don't work.

Under your logic

1) You accept that a 10kg object has double the force as a 5 kg object. But then you don't. But then you claim there is more than one definition of the word "force" (which isn't true above as I show).

2) You calculate a different acceleration for each object. This violates Galileo's claim (which you accepted) that two objects of different masses will fall at the same rate.

There are contradictions in your thinking. Newton's laws work without contradiction.

This also shows why math (which makes it so clear) is better than a bunch muddled words. As soon as you do the math, you can see whether you have it right or not.

2 Replies

@maxdancona,

maxdancona wrote:

You answered one of the three questions. And you are writing a lot of words... it boils down to this.

Under Newton's Laws

1) F = ma

2) F = G(Mm)/(r^2)

3) The meaning of the word "force" is the same in both of these equations. There is nothing to reconcile and no contradiction.You can plug in the number for yourself/

How about you plug in the numbers to the gravitational equation you posted above and show your results?

Quote:

1) You accept that a 10kg object has double the force as a 5 kg object. But then you don't. But then you claim there is more than one definition of the word "force" (which isn't true above as I show).

2) You calculate a different acceleration for each object. This violates Galileo's claim (which you accepted) that two objects of different masses will fall at the same rate.

There are contradictions in your thinking. Newton's laws work without contradiction.

This also shows why math (which makes it so clear) is better than a bunch muddled words. As soon as you do the math, you can see whether you have it right or not.

Let's discuss this after you plug in the numbers for the gravitational equation you posted above and show your results.

[/quote]

1 Reply

@livinglava,

If I do this for you.... will you just admit that you are wrong?

1) For F = GMm/r² I will plug in the numbers for the Gravitation constant, the mass of the Earth and radius of the Earth to get the force of gravity for each object (which I have already given).

2) I will use the value of F calculated above for each object with the equation a = F/m (algebraically equivalent to F = ma). I will plug in the mass of each object and the value of F to calculate the acceleration of gravity for each object.

3) I will show you that the accelerations are equal proving that Newton's laws match Galileos observation.

That should be enough. This is not that complicated. If they match, will you admit you are wrong?

1 Reply

The connection between Anti-Science and Anti-Education views.

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