What is the correct moment of inertia for part a using I=m*r^2?

[Sneakatone]

for part a I used the equation I=m*r^2 ---> 120(58/100)^2=40.36 kg*m^2

b)I know how to do this using the equation K=1/2Iw^2 but my moment of inertia is incorrect.

 

[SammyS]

for part a I used the equation I=m*r^2 ---> 120(58/100)^2=40.36 kg*m^2

b)I know how to do this using the equation K=1/2Iw^2 but my moment of inertia is incorrect.

What is the moment of inertia of a uniform disk of mass, M, and radius, R ?

 

[Sneakatone]

I used the equation 1/2MR^2 and got =20.18.
when I plugged everything into the KE equation I had 305.22 J but that is incorrect.

 

[SammyS]

I used the equation 1/2MR^2 and got =20.18.
when I plugged everything into the KE equation I had 305.22 J but that is incorrect.

What are the units for ω ?

 

[Sneakatone]

rev/s

 

[haruspex]

rev/s

The rotation rate is given you in rev/s, but what units does it need to be into plug it into the formula for KE?

 

[Sneakatone]

should it be rev/min or rad/s?

 

[Sneakatone]

I got it now it should be in rad/s for some reason I thought It was suppose to be rev/s.
Thank you all!