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# Speed of a feather and a bowling ball hitting the floor

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You hang up a feather in a special room. After the oxygen has been pumped out of the room, you release it. After a free fall of 2,25 seconds the feather hits the floor. Calculate the height of the fall. A bit afterwards you allow oxygen back into the room. You now hang up a bowling ball. The underside of the ball hangs at the same height as the feather of the previous experiment. You calculate the speed of the bowling ball hitting the floor. Is the speed greater, lesser or equal to the speed of the feather hitting the floor?

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Jan 10, 2020

#1
+107520
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When you say oxygen, I assume you really mean all gasses.

So the feather is falling in a vacuum and the bowling bowl is falling where there is air resistance.

I think the ball would fall more slowly.

Jan 10, 2020
#2
+1

Sorry I don't really know all the correct English terms in physics, but yes that's basically it :) It seemed more obvious to me that a feather would fall slower since well... it's a feather. But this also makes a lot of sense! I don't really have an idea on how to calculate the height since I only know the duration of the free fall but maybe someone else will come along and help me :D

Guest Jan 10, 2020
#3
+107520
+1

I do not know if you are supposed to do this with calculus or with physics formulas.

I usually use calculus

If you say up is positive direction then

acceleration = gravity = -9.8m/s^2

Initial speed is 0

initial height is h

After 2.25 secs the father falls h metres and is at a height of 0.

$$\ddot{x}=-9.8m/s^2\\ \dot{x}=-9.8t\;m/sec\\ x=\frac{-9.8t^2}{2}+h\;metres\\ when\;\;t=2.25\;\;x=0\\ 0=\frac{-9.8*2.25^2}{2}+h\\ 0=-24.80625+h\\ h=24.80625 metres.$$

If the feather was in a room full of air then I think it would drop a lot more slowly because of the air resistence.

I am not good at Physics but that sounds right to me.

Jan 10, 2020
#4
+1

Ah I see! Thank u so much :D

Guest Jan 10, 2020