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Verification: Hanging mass on cylinder. Moment of inertia

by pat666
Tags: cylinder, inertia, mass, moment, verification
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pat666
#1
May1-10, 12:00 AM
P: 709
1. The problem statement, all variables and given/known data
A 15.0 kg bucket of water is suspended by a very light rope wrapped around a solid cylinder 0.300 m in diameter with a mass of 12.0 kg. The cylinder pivots on a frictionless axle through its centre. The bucket is released from rest at the top of a well and falls 10.0 m to the water.
a) What is the tension in the rope while the bucket is falling? my answer: 42.15N
b) With what speed does the bucket strike the water? my answer: 11.8m/s
c) What is the time of the fall? my answer: 1.69s
d) While the bucket is falling, what is the force exerted on the cylinder by the axle: my answer: 159.87N this is the one that i am really unsure of (and a))

2. Relevant equations

solved but unsure

3. The attempt at a solution

could someone who knows what there doing please check my answers, i wouldn't ask if it wasn't important.. thanks in advance.
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ehild
#2
May1-10, 01:25 AM
HW Helper
Thanks
P: 10,626
It looks good. How did you get the force of the axle?

ehild
pat666
#3
May1-10, 01:45 AM
P: 709
actually that part was wrong, it is actually just F=ma and it turns out to be 105N i hope. ive actually been getting a lot of help from someone else on PF

pat666
#4
May1-10, 05:30 AM
P: 709
Verification: Hanging mass on cylinder. Moment of inertia

Hi, just a quick question. why do they give the radius of the cylinder if it is not needed, is there a way to solve these problems that does require the radius?
I have another very similar problem to this that i didnt use the radius for either
Squeezebox
#5
May1-10, 11:28 AM
P: 58
Quote Quote by pat666 View Post
Hi, just a quick question. why do they give the radius of the cylinder if it is not needed, is there a way to solve these problems that does require the radius?
I have another very similar problem to this that i didnt use the radius for either
They could be giving you extra info for you to sift through and see what's relevant and what's not.
kuruman
#6
May1-10, 01:31 PM
HW Helper
PF Gold
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P: 3,440
Quote Quote by pat666 View Post
Hi, just a quick question. why do they give the radius of the cylinder if it is not needed, is there a way to solve these problems that does require the radius?
I have another very similar problem to this that i didnt use the radius for either
If the problem gave you a pulley with a moment of inertia that cannot be calculated from a formula, then you do need the radius. However, the method is the same.


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