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Q & A: Dropping coins

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Most recent answer: 12/22/2009
Q:
If i have 2 coins hanging in the air at diffrent heights (let’s say like 15ft and 3ft), and i dropped the heighest one (15ft) and let it fall solo untill it reaches the lower one (that i realese when both coins are parralel) would the first coin hit the ground first and why? also is there more than 1 reason why if so please list.
- Jeffrey (age 12)
Kenosha,Wi
A:
Hi Jeffrey,

The one you dropped from a higher place should get there first if you release the lower one from rest just as the first one goes zooming past.

The reason is that when the first coin goes past the second coin, it's moving much faster than the second coin. Gravity will accelerate both coins at the same rate, but that's the rate of change of velocity. If you start out with some velocity to begin with, gravity will cause it to increase, but this velocity will still always be higher than something that starts at rest.

Imagine two coins falling from the same height. One is thrown downwards, while the other is just dropped. The one you throw downwards will get to the bottom first.

Tom

(published on 10/22/2007)

Follow-Up #1: two coins

Q:
Well, my teacher said that it is about the mass and how big it is.
- Steven V. (age 11)
Pennsylvania USA
A:
Steven- Are you sure that your teacher was thinking of the same problem described here? Maybe he was talking about something else. If not, this may be one of those cases where a teacher is wrong. Unfortunately, some teachers are very poorly educated in science.
The answer given in #188 is correct.

Mike W.


(published on 12/22/2009)

Follow-up on this answer.