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

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Discussion Overview

The discussion centers around the concept of gravity, particularly whether the force of gravity is influenced by an object's mass. Participants explore misconceptions related to gravity, the effects of gravity on different celestial bodies, and the implications of these ideas in educational contexts.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • Some participants express disbelief regarding a philosophy TA's understanding of gravity, suggesting that basic concepts should be intuitive for students.
  • There is a discussion about the gravitational force on the Moon being weaker than on Earth, with some participants speculating on the use of weighted boots to maintain a natural gait.
  • Participants present multiple-choice questions related to gravity and motion, indicating varying levels of understanding among students.
  • Some argue that an object's horizontal velocity does not affect its vertical velocity, while others challenge this claim by introducing hypothetical scenarios involving curvature of the Earth.
  • There are references to misconceptions in scientific education and the need for fundamental scientific knowledge among students.
  • The relevance of philosophical perspectives on scientific understanding is debated, with some participants questioning the usefulness of such perspectives in grasping basic physics concepts.

Areas of Agreement / Disagreement

Participants do not reach a consensus; multiple competing views remain regarding the understanding of gravity and its implications in educational settings. Disagreements arise over the interpretation of gravity's effects and the adequacy of scientific education.

Contextual Notes

Some participants highlight the limitations of educational curricula in the U.S., suggesting that foundational knowledge about gravity may not be adequately covered before college. There are also unresolved questions about the specifics of gravitational effects in different contexts.

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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.
 

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