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This question has been asked multiple times here and all over the internet yet I can't find a conclusive answer:

Which one is the right one?

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mahos
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    Fun experiment: do what Galileo did and throw two identical shaped but different material objects from a height and see what happens – pho Nov 30 '13 at 23:11
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    @PranavHosangadi please read the answers of the questions mentioned in my question – mahos Nov 30 '13 at 23:22
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    @MartinBeckett I already mentioned that question above along with another one on this site that claims the opposite ,that is why I'm asking this – mahos Nov 30 '13 at 23:23
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    @mahos - sorry I noticed that but there is no way to withdraw a dupe flag. – Martin Beckett Nov 30 '13 at 23:48
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    @mahos, I have read then, but the best way to find what is the right one is to do it for yourself. Unless you're willing to take someone's word for it. In which case you've got to choose which one makes more sense to you – pho Dec 01 '13 at 05:13

2 Answers2

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Suppose you pick two people at random. From one, you pluck a single hair from their head. Is it possible to tell who had the hair plucked by weighing the people?

Technically, plucking a hair makes a person very slightly lighter, so you get a tiny bit of information about who had the hair plucked by weighing the people. But the information is very slight because the effect is so small that for practical purposes it may be ignored.

Similarly, heavier objects are mathematically predicted to collide with Earth very slightly faster because of their gravitational effect on the Earth. But the effect is so preposterously small as to be meaningless, so it commonly ignored.

The answers you linked don't disagree with each other. One isn't right and the other wrong. They simply need to be interpreted in their own context. People don't try to account for every little possible influence, like whether a hair was plucked from someone's head or whether they've trimmed their fingernails recently when talking about a human's weight. Similarly, they don't always try to account for every tiny phenomenon and make every statement perfectly precise when they talk about physics.

Mark Eichenlaub
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  • what about this part of the answer to the second questions "•The heavier an object is, the stronger its resistance to an accelerating force will be: Heavier objects are harder to set in motion, meaning that for the same acceleration you need a larger force.

    When people think that heavy objects should fall faster, they only think of the first point. But in reality, the first and second point cancel out each other: Yes, the earth pulls stronger on a heavy object, but the heavy object is more reluctant to get moving " "cancel each other out"?

     – mahos Nov 30 '13 at 23:27
  • What about it? It's a correct statement. What do you want to know? Be more specific. – Mark Eichenlaub Nov 30 '13 at 23:28
  • shouldn't that mean that the inertia cancels the effect extremely tiny added acceleration resulting in the same objects falling exactly at the same speed ? – mahos Nov 30 '13 at 23:31
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    No. The claim that heavier objects fall faster is not a claim that they have greater acceleration at a given distance from the Earth when viewed in an inertial frame. If you read the answers to the question you already linked, this is made clear. – Mark Eichenlaub Nov 30 '13 at 23:49
  • @mahos, you seem to be thinking about the accelerating force only on the "falling" objects. The difference comes when you realize that the Earth is also a "falling" object and it also receives an accelerating force. This is why knowing the reference frame is absolutely crucial when discussing "falling"--because really, you're looking at "closing speed" which includes the acceleration of the object and Earth, not just the acceleration of the "falling" object. – ErikE May 22 '15 at 22:56
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In one sentence:

More mass means stronger attraction and less buoyancy (they fall faster), but the effect is negligible in most cases.

jinawee
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