How Fast Does the Rim of a Spinning Disk Travel?

AI Thread Summary
To determine the speed of a point on the rim of a spinning disk, the kinetic energy formula K=(1/2)*I*(ω^2) is used, where I is the moment of inertia and ω is the angular velocity. The moment of inertia for a thin disk is calculated as I=(1/2)*M*R^2. The user encounters difficulties in calculating the correct angular velocity and converting it to linear speed. There is a realization of a potential calculation error, prompting a reconsideration of the approach. The discussion highlights the importance of correctly applying formulas and unit conversions in physics problems.
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Problem 13.30
A thin, 60.0g disk with a diameter of 7.00 cm rotates about an axis through its center with 0.240 J of kinetic energy. What is the speed of a point on the rim?

Homework Equations


m=.06kg
r=.035m
KE=.240J

The Attempt at a Solution



K=(1/2)*I*(w^2)
I=(1/2)*M*R^2

I'm using the formula above but I'm not getting the right answer. My numbers seem way to small. I eventually get w(omega) alone. Where do I go from here. Do i need to solve for the length to figure out rad/s then convert to m/s?

Perhaps I am approaching this wrong.
 
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Calculation error, sorry. Mods you can delete.
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
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Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
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