Verification: Hanging mass on cylinder. Moment of inertia

AI Thread Summary
The discussion revolves around a physics problem involving a falling bucket of water suspended by a rope around a solid cylinder. The user presents their calculations for the tension in the rope, the speed of the bucket upon impact, the time of fall, and the force exerted on the cylinder by the axle, seeking validation for their answers. While the initial force on the axle was incorrectly calculated, it was later corrected to 105N using the formula F=ma. Participants note that the radius of the cylinder may not always be necessary for solving such problems, but it can be relevant in cases involving moment of inertia. The conversation emphasizes the importance of discerning which information is pertinent to the problem at hand.
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Homework Statement


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))

Homework Equations



solved but unsure

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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It looks good. How did you get the force of the axle?

ehild
 
actually that part was wrong, it is actually just F=ma and it turns out to be 105N i hope. I've actually been getting a lot of help from someone else on PF
 
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
 
pat666 said:
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.
 
pat666 said:
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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Thread 'A cylinder connected to a hanging mass'

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