Is the force of gravity affected by an object's mass?

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The discussion revolves around misconceptions about gravity, particularly in relation to the Moon, sparked by a philosophy TA's apparent misunderstanding of basic physics. Participants express disbelief that a college-level educator could make such an error, emphasizing that all objects with mass exert gravitational force, including on the Moon. A series of hypothetical physics questions are posed, highlighting the confusion surrounding gravitational concepts and the importance of basic scientific literacy.The conversation also touches on the quality of science education in the U.S., with some arguing that mandatory science education often ends after 9th grade, leading to gaps in knowledge among college students. Participants share anecdotes about testing students' understanding of gravity and related concepts, revealing a concerning level of scientific ignorance. The need for a foundational understanding of physics is emphasized, as well as the potential for developing a questionnaire to assess scientific knowledge across various disciplines. Overall, the thread underscores the significance of basic scientific education and the implications of widespread misconceptions in society.
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Clearly that TA never took a physics course. Of course there is gravity on the moon. All objects exert their own gravitational force by virtue of the fact that they are comprised of matter.
 
Yes, I believe there really are people that stupid.
 
He forgot to ask the follow-up question.

If you spin a bicycle tire (on Earth) and suspend one end of the axle from a rope loop, so the tire's spin moves same direction as your curled fingers as your thumb points from the suspended end of the axle to the free side of the axle, which direction will the tire move?

a) the free end of the axle will rotate downward until the tire falls out of the rope loop.
b) the free end of the axle will rotate upward until the tire falls out of the rope loop.
c) the axle will rotate counter-clockwise around the rope loop (as you look down toward the tire)
d) the axle will rotate clockwise around the loop (as you look down toward the tire)
 
Wow...clearly I haven't been hanging out with enough non-physics people.
 
russ_watters said:
That a philosophy TA made a basic physics error on an issue an average 8th grader should know intuitively? Yeah, I believe that.

8th grader? Try college student!

above link said:
I put two multiple choice questions on my Physics 111 test, after the study of elementary mechanics and gravity.

13. If you are standing on the Moon, and holding a rock, and you let it go, it will:
(a) float away
(b) float where it is
(c) move sideways
(d) fall to the ground
(e) none of the above

The first question was generally of average difficulty, compared with the rest of the test: 57% got it right.
 
russ_watters said:
That a philosophy TA made a basic physics error on an issue an average 8th grader should know intuitively? Yeah, I believe that.

No, I was wondering if the TA was right about the heavy boots. :biggrin:
 
Pupil said:
No, I was wondering if the TA was right about the heavy boots. :biggrin:

Since the gravitational force on the moon is weaker than on Earth they may well have used weighted boots to maintain a more natural gait. Obviously this doesn't mean they would have floated away otherwise. I am also unsure if such a thing was actually done.
 
  • #10
...
That's pretty sad.

I wonder, though, if there aren't similar misconceptions we all have about certain scientific things. I would hope that they wouldn't be this bad.

What basic, fundamental scientific knowledge should every educated person have? Can we try making posts that contain nuggets of wisdom which, once compiled, people can study in order to avoid gaffes like this? I'll go first.
 
  • #11
Every object with mass exerts a gravitational force on every other object with mass in the universe.
 
  • #12
We had a lecturer who was very well known for her lack of knowledge on the subject. Once she was mentioning some angle between two objects is x degrees. One student wanted to make fun on her and asked a question - is it degree celsius or Fahrenheit? She got very confused and told she needs to refer and get back later.

Your TA is a genius compared to her :)
 
  • #13
An objects horizontal velocity has no effect on its vertical velocity. For example, a ball dropped and a bullet fired horizontally from a gun will hit the ground at the same time (if both objects are at the same height)
 
  • #14
cristo said:
8th grader? Try college student!

No, he meant even an 8th grader should know the correct answer.
 
  • #15
Hammer, feather, moon.
 
  • #16
An objects horizontal velocity has no effect on its vertical velocity. For example, a ball dropped and a bullet fired horizontally from a gun will hit the ground at the same time (if both objects are at the same height)
Not necessarily. If the gun was powerful enough, the bullet would travel far enough for the ground to curve away from it, so that the ball would actually hit the ground first.
 
  • #17
I was in a philosophy class

no surprise there. the sad thing is that this may be a person planning to pursue a law degree.
 
  • #18
Tibarn said:
Not necessarily. If the gun was powerful enough, the bullet would travel far enough for the ground to curve away from it, so that the ball would actually hit the ground first.

Who said anything about a curved ground? I'm firing my gun in Flatland, where the ground is flat. If I said anything about the specifics of the planet Earth, I would have used the word tangential, not horizontal.
 
  • #19
Who said anything about a curved ground? I'm firing my gun in Flatland, where the ground is flat. If I said anything about the specifics of the planet Earth, I would have used the word tangential, not horizontal.
Are you referring to the Flatland from the eponymous book, which as I recall is two-dimensional? Or perhaps Either way, if you're on a flat torus, the bullet might never hit the ground. There's also the question of whether the gravitational field is uniform. If you won't do things on Earth, at least be more specific.
 
  • #20
Does it matter whether objects falls or floats away on the moon surface?

But they shouldn't use things as facts for which they are ignorant IMO.

(I remember once getting into arguments with one arts teacher for something similar. I gave up :p)
 
  • #21
rootX said:
Does it matter whether objects falls or floats away on the moon surface?
Does it matter what a philosophy student thinks?
 
  • #22
mgb_phys said:
Does it matter what a philosophy student thinks?

No because they don't think anything useful.
 
  • #23
cristo said:
8th grader? Try college student!
I think you misunderstood what I was getting at: I realize the issue was posed to college students. I pulled the "8th grader" thing out of the air, but it is based on 8th grade being where one gets their first exposure to the concept of how gravity works. Once you know a couple of facts (gravity comes from mass, the moon has less mass than the earth), the issue becomes ridiculously simple.

I know the people polled were college students: they should be more than qualified to answer this question. Editorially, it is unfortunate, but mandatory science education in the US basically ends after 9th grade, iirc. Kids looking toward a scientific background take science classes in high school, but they aren't required. So a week or two about Newtonian physics in 8th grade might be all an American student ever sees.

I'm not sure where the disconnect lies exactly, but this issue is so simple (see the two facts required, above) that a philosophy class - where someone theoretically learns logic - should be sufficient for figuring this out.
 
  • #24
rootX said:
Does it matter whether objects falls or floats away on the moon surface?

it matters to the moon. and to the earth, too. were it to drift away a grain at a time, we would soon have no tides, no nightlight, and no signal that many species depend on for breeding.
 
  • #25
Proton Soup said:
it matters to the moon. and to the earth, too. were it to drift away a grain at a time, we would soon have no tides, no nightlight, and no signal that many species depend on for breeding.

Restating the question for further clarification:
Does it matter "everyone knowing" whether objects falls or floats away on the moon surface?
 
  • #26
Pupil said:
An objects horizontal velocity has no effect on its vertical velocity. For example, a ball dropped and a bullet fired horizontally from a gun will hit the ground at the same time (if both objects are at the same height)

Try telling that to the airplane wing.
 
  • #27
rootX said:
Restating the question for further clarification:
Does it matter "everyone knowing" whether objects falls or floats away on the moon surface?

it matters to me. these are the same people that follow the current global warming hypothesis like sheep.
 
  • #28
How about this these,

1) Does it really matter if your boss thinks the world is flat?
2) Is that really ANY LESS stupid than thinking the moon has no gravity?
 
  • #29
rootX said:
Does it matter "everyone knowing" whether objects falls or floats away on the moon surface?

Who joins a Physics Forum whose blood doesn't run cold when they hear about rampancy of basic scientific ignorance?
 
  • #30
Proton Soup said:
it matters to me. these are the same people that follow the current global warming hypothesis like sheep.

Refer to the original post and I am not different in that case:
But they shouldn't use things as facts for which they are ignorant IMO.

junglebeast said:
How about this these,

1) Does it really matter if your boss thinks the world is flat?
2) Is that really ANY LESS stupid than thinking the moon has no gravity?

DaveC426913 said:
Who joins a Physics Forum whose blood doesn't run cold when they hear about rampancy of basic scientific ignorance?

I wouldn't spend all my day arguing with those people or trying to find ignorance in other people. There are lot better things to do.
 
  • #31
DaveC426913 said:
Who joins a Physics Forum whose blood doesn't run cold when they hear about rampancy of basic scientific ignorance?

http://www.nsf.gov/statistics/seind04/c7/fig07-06.htm
 
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  • #32
rootX said:
I wouldn't spend all my day arguing with those people or trying to find ignorance in other people. There are lot better things to do.

Like spending all day arguing with people about how unimportant science knowledge is to the everyman?
 
  • #33
rootX said:
I wouldn't spend all my day arguing with those people or trying to find ignorance in other people. There are lot better things to do.
But you might spend all day living in the country that they are president of. Doesn't that give you the wigglies?
 
  • #34
mgb_phys said:
http://www.nsf.gov/statistics/seind04/c7/fig07-06.htm

Question #2
Does the Earth go around the Sun, or does the Sun go around the Earth?

I understand the rules about linking to unvetted information sources, but in this case does the National Science Foundation know best or https://www.physicsforums.com/showthread.php?t=245334"?
 
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  • #35
Phrak said:
I understand the rules of linking to unvetted websites, but in this case does the National Science Foundation know best or https://www.physicsforums.com/showthread.php?t=245334"?

Thank god I don't live in those countries.

Oh crap...

You should be required to know the answers to at least most of those questions to hold public office. Then again that might bring government to a standstill.
 
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  • #36
Is there gravity on the moon?

Well of course there is. If you would ask any person walking down the street, they would most likely say yes. It's just that Earth's gravity is a little bit more stronger, hence more weight is presentable, but same mass as it is on the moon.
 
  • #37
jhooper3581 said:
Is there gravity on the moon?

Well of course there is. If you would ask any person walking down the street, they would most likely say yes. It's just that Earth's gravity is a little bit more stronger, hence more weight is presentable, but same mass as it is on the moon.

Are you sure it's not an ill posed question. If so, how could you answer to the negative?
 
  • #38
Phrak said:
Are you sure it's not an ill posed question. If so, how could you answer to the negative?
Well, during my lifetime most people have said there's gravity presentable on the moon, so I thought it would be a common sense thing. Maybe I didn't prove it more throughly. And what do you mean by negative? Like: Is there no gravity on the moon?
 
  • #39
Phrak said:
Question #2
Does the Earth go around the Sun, or does the Sun go around the Earth?

I understand the rules about linking to unvetted information sources, but in this case does the National Science Foundation know best or https://www.physicsforums.com/showthread.php?t=245334"?

Did you think this was a crackpot link......^....above. Or maybe something like the Physics Forum?
 
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  • #40
jhooper3581 said:
Well, during my lifetime most people have said there's gravity presentable on the moon, so I thought it would be a common sense thing. Maybe I didn't prove it more throughly. And what do you mean by negative? Like: Is there no gravity on the moon?

1) Is there gravity if you are freely falling?

2) What is gravity? Does it mean a force like gravitational attraction or are they speaking of the general phenomena of gravity, where one such phenomenon is gravitational attraction.

I should admit that it could be a well posed question for 12th graders, but 'gravity' is a not a good replacement for 'gravtitional attraction' when speaking to physicists.
 
  • #41
Phrak said:
1) Is there gravity if you are freely falling?

2) What is gravity? Does it mean a force like gravitational attraction or are they speaking of the general phenomena of gravity, where one such phenomenon is gravitational attraction.

I should admit that it could be a well posed question for 12th graders, but 'gravity' is a not a good replacement for 'gravtitional attraction' when speaking to physicists.
Well, I've just graduated from high school not too long ago, and I took basic physics class in junior year. For the first question, if you are free falling, then isn't there still gravity left, because someone can determine the speed of falling, due to gravity. I don't know haha
 
  • #42
russ_watters said:
Editorially, it is unfortunate, but mandatory science education in the US basically ends after 9th grade, iirc. Kids looking toward a scientific background take science classes in high school, but they aren't required.

Really? I just presumed that students had to take basic classes in all subjects during high school. Over here, the bare minimum that you have to take until the end of compulsory schooling (at 16) are english (lit & lang), maths and science. Do US students get to take whatever they want? This is presumably the reason why US colleges have the general education courses that students have to take. It seems pretty backwards to me!
 
  • #43
That's refreshing to see that US respondents were scientifically competitive with their European counterparts.

It looks like the US was a little weaker in the life sciences, and a little stronger in the physical sciences.

I wonder what a comparison of mathematical knowledge would demonstrate.
 
  • #44
russ_watters said:
I know the people polled were college students: they should be more than qualified to answer this question. Editorially, it is unfortunate, but mandatory science education in the US basically ends after 9th grade, iirc. Kids looking toward a scientific background take science classes in high school, but they aren't required. So a week or two about Newtonian physics in 8th grade might be all an American student ever sees.

I don't think you recall correctly. Most high schools if not all will require a year of physics chemistry and biology or something similar (required by the state the high school is in)
 
  • #45
In my state high school students are required to take a year of chemistry, a year of physics, and a year of biology (6 semesters), along with four years of math (8 semesters).
 
  • #46
I don't buy this story. It was convincing 'til here:

To prove my point, we went back to our dorm room and began randomly selecting names from the campus phone book. We called about 30 people and asked each this question: 1

1. If you're standing on the Moon holding a pen, and you let go, will it
a) float away,
b) float where it is,
or c) fall to the ground?

About 47 percent got this question correct.

Call strangers at random with a question like this, and at leat 80% will answer "WHAT!? I'm on the no-call list. Call me again and I'll SUE!"

:biggrin:
 
  • #47
CRGreathouse said:
In my state high school students are required to take a year of chemistry, a year of physics, and a year of biology (6 semesters), along with four years of math (8 semesters).

When I was in high school, a little over a decade ago, we were only required two years of science (physics and biology) and three years of math.
 
  • #48
CRGreathouse said:
In my state high school students are required to take a year of chemistry, a year of physics, and a year of biology (6 semesters), along with four years of math (8 semesters).
That was the requirement when I went to high school in Texas during the 1970's. Biology (10th grade), Chemistry (11th grade), and Physics (11th or 12th) grade. There was a general science course in 9th grade, which was more or less introductory physics/chemistry with a broad basis. Mathematics was taught every year from 7th through 12th grade, but 7th and 8th were fairly redundant.

9th grade was Algebra I
10th grade Geometry
11th grade Algebra II (some analytical geometry)
12th grade Analytical Geometry and Calculus

My 10th grade honors Geometry course was taught in one semester, so we the Trignometry course during the second semester. Unfortunately, our 10th math teacher burned herself out (exhaustion) by the end of the first semester, and we got a different teacher who wasn't quite as intense as the first teacher.


I'm pretty sure I learned about tides as early as 6th grade. Tides are affected by Sun AND Moon by virtue of gravity.

Of course, all education is not equal, and all students are not equal.
 
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  • #49
matthyaouw said:
I don't buy this story.
Me either. Too many people know about that hammer vs feather video for this story to be believable.
 
  • #50


Note that the people inside the moonbase not equipped with those special heavy boots just float. The end scene shows that the heavy boot effect has limited applicability. Slap someone in the back and off he goes, only to get hit by a meteor streaking through the moon's thick atmosphere. Documented!
 
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