dropping balls

[Joe Ross]

If you were to drop two racquetballs, one filled with lead and the
other normal, off of the Sears Tower, which one would hit the ground
first?

A) neglecting air resistance
B) including air resistance
C) Does the answer change for either A or B if one ball is many orders of magnitude heavier then the other.

I was wrong the first time I tried to answer this question, and it spawned a 100+ post thread at another forum.

[Alex Cormier]

Originally Posted by Joe Ross

If you were to drop two racquetballs, one filled with lead and the
other normal, off of the Sears Tower, which one would hit the ground
first?

A) neglecting air resistance
B) including air resistance
C) Does the answer change for either A or B if one ball is many orders of magnitude heavier then the other.

I was wrong the first time I tried to answer this question, and it spawned a 100+ post thread at another forum.

i say they drop the same time...

[Wayne C.]

Didn't Galileo already do this?







I thought I saw him at the Sears Tower.....

[RogerR]

Originally Posted by Joe Ross

If you were to drop two racquetballs, one filled with lead and the
other normal, off of the Sears Tower, which one would hit the ground
first?

A) neglecting air resistance
B) including air resistance
C) Does the answer change for either A or B if one ball is many orders of magnitude heavier then the other.

I was wrong the first time I tried to answer this question, and it spawned a 100+ post thread at another forum.

A) both hit at same time
B) the one filled with lead
C) no

[Adam Y.]

If you were to drop two racquetballs, one filled with lead and the

Hmm... I'd say they never hit the floor. They would get stuck midway. Of course neglecting air resistance I would say they would hit at the same time.

[Andy Baker]

a. the same
b. the same
c. no


They are the same shape and therefore have the same terminal velocity.

Andy B.

[Alan Anderson]

Originally Posted by Andy Baker

They are the same shape and therefore have the same terminal velocity.

Sorry, Andy, but terminal velocity also depends on density. A lead-filled sphere will have a higher terminal velocity than an air-filled one. Try dropping a ping-pong ball and a rubber ball of the same size -- the ping-pong ball reaches terminal velocity very quickly, but the rubber ball keeps accelerating and outpaces it.

The answer to the question is that air resistance matters when the two objects' densities are different. A heavier ball having the same size as a lighter one will hit the ground first, if you drop them from high enough for the lighter one to reach terminal velocity.

[Andy Baker]

Originally Posted by Alan Anderson

Sorry, Andy, but terminal velocity also depends on density. A lead-filled sphere will have a higher terminal velocity than an air-filled one. Try dropping a ping-pong ball and a rubber ball of the same size -- the ping-pong ball reaches terminal velocity very quickly, but the rubber ball keeps accelerating and outpaces it.

The answer to the question is that air resistance matters when the two objects' densities are different. A heavier ball having the same size as a lighter one will hit the ground first, if you drop them from high enough for the lighter one to reach terminal velocity.

Thanks, Alan... it is a good thing that I'm not designing airplanes!

I'm glad to be on the same team as smart people.


Andy B.

[FizMan]

Can you link us to this 100 post thread on the other forum?

[Joe Ross]

Originally Posted by FizMan

Can you link us to this 100 post thread on the other forum?

I will once things have died down here

[Adam Y.]

Put simply: horizontal components of projectile motion act independantly of vertical component

Ummm... Not neccessairly. I was thinking of the myth of dropping a penny off the empire state building. The wind from the top of the building actually forces the penny to the side of building thus slowing it down. Im not sure how it would affect a larger object such as a ball but if it is strong enough to forceit up against the building then yes it will have an effect.

[Christina]

Originally Posted by Andy Baker

Thanks, Alan... it is a good thing that I'm not designing airplanes!

Hmm...I'm designing airplanes (careful if any of you have the opportunity to fly in a plane that I have worked on...though you'd have to be in the Navy)...does that mean I should be able to answer this question?


Well, I don't have my aero books on me (I left them at school) but all those equations Chris was spouting out sure does look familiar. So, lets see...if I had to answer them, my answers would be:

A) the same
B) the lead filled ball
C) no, they don't change

[spears312]

well, I would say A) the same time B) the lead one first and C) no

BUT, it doesn't say that they are dropped at the same time, so it could be A) which ever you dropped first B) which ever you dropped first unless you dropped the lead filled almost instantly after the normal and C) would remain the same.

but then I was thinking... is there a point on the tower which you can drop something so that it will go straight down to the ground?

[Adam Y.]

All of you are neglecting one thing and that's the fact that there should be pretty good cross winds when you drop the balls due to the effects of being ina city. This is the same reason why pennys never reach the bottom of the Empire State building. Im not sure how powerful these winds are but they might affect the outcome.

[RogerR]

Originally Posted by Adam Y.

All of you are neglecting one thing and that's the fact that there should be pretty good cross winds when you drop the balls due to the effects of being ina city. This is the same reason why pennys never reach the bottom of the Empire State building. Im not sure how powerful these winds are but they might affect the outcome.

cross winds would have a more dramatic effect on the lighter of the two balls, and therefore wouldn't affect which one would reach the ground first. now if there was a powerful enough downdraft, and it was a relativly short drop, maybe the lighter of the two would hit the ground first.