Does Newton's Third Law Explain the Different Fall Rates of Water and Glass?

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Discussion Overview

The discussion revolves around the question of whether a glass of water falls slower than the glass itself when dropped from a height, considering factors such as air resistance and the effects of Newton's Third Law. The scope includes conceptual reasoning and exploratory arguments related to physics principles.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that the water would lift from the bottom of the glass and fall slower than the glass, while others argue that air resistance would affect the fall rate of the glass.
  • One participant asserts that on Earth, in the absence of air resistance, all objects fall at the same rate regardless of their weight, suggesting that both the glass and water would hit the ground simultaneously.
  • Another participant shares an example of a physics demonstration where a book and a piece of paper fall at different rates until the paper is placed on the book, illustrating the effects of air resistance.
  • Some participants note that the glass acts as a barrier against air friction, which could influence the fall rate of the water contained within it.
  • One contribution suggests that if the glass were to fall upside down, the water would exert force on the inner base of the glass, potentially leading to different fall rates based on surface area and weight considerations.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the effects of air resistance and the implications of Newton's Third Law on the fall rates of the glass and water. The discussion remains unresolved, with no consensus reached on the specific dynamics involved.

Contextual Notes

Limitations include assumptions about air resistance, the orientation of the glass during the fall, and the specific conditions under which the experiment is conducted. These factors remain unresolved within the discussion.

mrcore64
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Hello!
We often have lots of free time on our hands at work when we should be er... working, anyway we use this time to debate questions that none of us are qualified to answer in a 'I'm 110% right B***H' way. So I decided to come here and post a couple of the ones we have been arguing in the hope that someone who knows his s**t can give us a 'I'm 110% right B***H' answer...

Todays one was...
'If you drop a glass of water off a building and ensure it falls straight, would the water fall slower than the glass?'

Cheers!

P.S*Sorry about the title of the thread it has nothing to do with this question! lol
 
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Well think about it, under what circumstances would one part fall slower?
 
Err if erm the... No, lol I have no idea!
Basicaly my argument is that the water would lift from the bottom of the glass and therefore fall slower and hit the ground after the glass...

My mate(Alex) thinks that the air resistance would cause the glass to fall slower which would hold the water from being able to fall faster so the glass would still contain the water when it hits the ground...

I'd like to point out at this point I know physics like *Keanu Reeves knows Shakespeare
 
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mrcore64 said:
I'd like to point out at this point I know physics like Keanu Reaves knows Shakespeare
LOL, I don't even know who Keanu Reaves is. :smile:
 
lol indeed... I meant Reeves! S**T
 
mrcore64 said:
Basicaly my argument is that the water would lift from the bottom of the glass and therefore fall slower and hit the ground after the glass...

My mate(Alex) thinks that the air resistance would cause the glass to fall slower which would hold the water from being able to fall faster so the glass would still contain the water when it hits the ground...

Your friend Alex is more right than you although his statement isn't 100% correct. Close though. It really wouldn't matter if there was air resistance or not for this experiment. On Earth (taking out air friction) and anywhere else there is gravity, everything falls at the same rate. If you were to take a 100 pound ball and a 50 pound ball and drop them from the same height at the same time, they both would hit the ground at the same time. So picture a cup of water in your hand. The water sits at the bottem of the cup. When you drop the cup both the cup and water accelerate towards the Earth at the same time.

To comfirm your experiment just get a paper cup, fill it with water and drop it and try to see what happens.
 
I think one of the best examples I've seen is this one.

My professor dropped our physics book and a piece of paper at the same time. The book fell to the group the fastest. Then he placed a piece of paper on the book, and they fell at the same rate. Thus :D Victory for physics.
 
Oops, I dropped my drink.

mrcore64 said:
Hello!
We often have lots of free time on our hands at work when we should be er... working, anyway we use this time to debate questions that none of us are qualified to answer in a 'I'm 110% right B***H' way. So I decided to come here and post a couple of the ones we have been arguing in the hope that someone who knows his s**t can give us a 'I'm 110% right B***H' answer...

Todays one was...
'If you drop a glass of water off a building and ensure it falls straight, would the water fall slower than the glass?'

Cheers!

P.S*Sorry about the title of the thread it has nothing to do with this question! lol

A glass of water dropped straight and upright would arrive at the ground as it left the top. How can I know that? Well, from Galileo I know that all objects fall at the same rate, barring air resistance. So without air we know that the glass will fall together. If we add air resistance then we see that the glass gets slowed down to some extent and would fall more slowly but, since the water is confined by the glass and cannot fall faster, they stay together. Right?
 
Well, the glass acts as a barrier against air friction. At the same time, the water can't go faster than the glass. This means that the glass slows down the water, so they both fall at the same time and in harmony.
 
  • #10
I get the feeling based on how the problem was stated, that air resistance should be taken into account. If the glass falls upright and doesn't rotate, of course the glass will hit the ground with the water still in it.
 
  • #11
when air resistance is not negligible
actually the water will be slower than the glass based on surface area and the glass assumed to have greater weight than total weight of water(under circumstance that the glass fall upside down position). and then the water exert force to the inner base of the glass ( explanation through Newton's third law)
if the glass fall in another style ( not up side down) the glass will have more surface area than the water, in this case air resistance for water is zero (hence falling at exactly 9.81 ms^-2). such as the glass will be slower than water. and with around the same reasoning as previous case, we normally see both fall at the same rate.
sorry my English sux
 
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