Mass and free fall question


by tengtou
Tags: fall, free, mass
tengtou
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#1
Feb7-08, 10:23 PM
P: 4
A ball of mass .5 kg is dropped from a height of 5 m. What is the greatest velocity it will have just before hitting the ground?

vf squared = vi squared + 2ad

vf squared = 0 squared + 2(9.8)(5)

vf = 9.8 m/s

So the greatest velocity is 9.8 m/s, right?

I am still very confuzzled and I think this is the right answer because where did the mass go? Or it doesn't even matter? Can someone verify?

Thanks!
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rl.bhat
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#2
Feb7-08, 10:55 PM
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Yes. Mass does not matter in the free fall under gravity. All the body get accelerated equally.
Dick
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#3
Feb7-08, 10:57 PM
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Welcome to the forums! No, mass doesn't matter. The acceleration downwards is g, independent of mass, ask Galileo. It's a purely kinematical problem.

tengtou
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#4
Feb7-08, 11:00 PM
P: 4

Mass and free fall question


Thanks! So is my answer correct?
Dick
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#5
Feb7-08, 11:07 PM
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Approximately, yes. I would round the answer to 9.9m/sec. But that's a detail.
tengtou
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#6
Feb7-08, 11:08 PM
P: 4
Sweet! Thanks!
tengtou
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#7
Feb7-08, 11:14 PM
P: 4
I don't know why the question had mass in it. Trick question or something haha.
Dick
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#8
Feb7-08, 11:29 PM
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In real world problems YOU have to figure out what's important and what isn't. It's just practice.


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