Angular velocity

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A torque of 10 N m is applied to a 10 kg disk of radius 0.2 m initially at rest. What is the angular acceleration of the disk?

I used I=1/2mr^2 so
1/2*10*0.2^2=.2

10Nm/0.2= 50 rad/s^2???

(With regard to the previous problem) The applied torque of 10 N m gets the disk rotating starting from rest. What is the angular velocity of the disk about an axis through its center, after it has completed two revolutions?
 

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  • #2
tiny-tim
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hi tica86! :smile:

(have a theta: θ an omega: ω and an alpha: α and try using the X2 icon just above the Reply box :wink:)
A https://www.physicsforums.com/library.php?do=view_item&itemid=175" of 10 N m is applied to a 10 kg disk of radius 0.2 m initially at rest. What is the angular acceleration of the disk?

I used I=1/2mr^2 so
1/2*10*0.2^2=.2

10Nm/0.2= 50 rad/s^2???
looks good! :biggrin:
(With regard to the previous problem) The applied torque of 10 N m gets the disk rotating starting from rest. What is the angular velocity of the disk about an axis through its center, after it has completed two revolutions?
you have ωi α and t, and you want θ …

(that's like having vi a and t, and wanting s)

so use the angular version of one of the standard https://www.physicsforums.com/library.php?do=view_item&itemid=204" equations :wink:
 
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  • #3
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hi tica86! :smile:

(have a theta: θ an omega: ω and an alpha: α and try using the X2 icon just above the Reply box :wink:)


looks good! :biggrin:


you have ωi α and t, and you want θ …

(that's like having vi a and t, and wanting s)

so use the angular version of one of the standard https://www.physicsforums.com/library.php?do=view_item&itemid=204" equations :wink:
Ok, so I tried 4*3.14=12.56
12.56^2/2*50rad/s^2= 1.57
square root=12.60??
Is that correct?
 
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  • #4
tiny-tim
Science Advisor
Homework Helper
25,832
251
hi tica86! :smile:

(have a square-root: √ and a pi: π and please use the X2 tag just above the Reply box :wink:)
12.56^2/2*50rad/s^2= 1.57
square root=12.60??
uhh? :redface: what formula are you using? :confused:
 

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