Light as a feather

  • Thread starter tatiana
  • Start date
  • #1
43
1

Main Question or Discussion Point

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
115
1
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
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
20,799
4,536
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
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
43
1
Your all right i forgot that were dealing with air resistance and were not in a vacuum
 

Related Threads on Light as a feather

  • Last Post
Replies
5
Views
770
Replies
13
Views
775
  • Last Post
Replies
7
Views
3K
Replies
13
Views
1K
  • Last Post
Replies
1
Views
1K
Replies
3
Views
2K
Replies
25
Views
4K
Top