Light as a feather

  • Thread starter tatiana
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  • #1
tatiana
43
1
I have a serious question, in all seriousness.. So you know how the theory says "if you dropped a piano and a penny off of the empire state buliding they would hit the ground at the same time" Well i was thinking and i wanted to know what would cause this not to be true.. when a coffe cup is empy this does not apply, neithe rif one of these objects were a feather?!?!
 

Answers and Replies

  • #2
Kracatoan
115
2
If you were in a vacuum, then yes, they would take the same time to hit the ground. But seeing as we're not, air resistance comes into play, slowing the time of descent.
 
  • #3
schip666!
595
0
If you pumped all the air out of NYC -- which some folks believe to be the case already -- and dropped a piano, penny, cup of coffee, and feather, they would all land at the same time. Under more normal circumstances the wind resistance of each object would need to be taken into consideration so, for instance, the feather might never make it to the ground (at least where you could find it easily).

I'm not sure that the fill-state of the coffee cup would make much difference though.
 
  • #4
Drakkith
Staff Emeritus
Science Advisor
21,987
6,049
In general, objects dropped in the atmosphere will not hit the ground at the exact same time due to drag. The difference between objects that aren't very light is not usually great enough that you would be able to tell a difference normally however. In a perfect vacuum everything would fall at the same rate since there would not be any drag.
 
  • #5
DaleSwanson
352
2
As the others said it's the air that slows the feather down. Specifically, it's because the feather has a much higher ratio of surface area to mass.

Apollo 15 famously showed this on the moon (a vacuum), by dropping a feather and a hammer.
http://www.youtube.com/watch?v=5C5_dOEyAfk"
 
Last edited by a moderator:
  • #6
tatiana
43
1
Your all right i forgot that were dealing with air resistance and were not in a vacuum
 

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