Calculate Angular Velocity after Star's Diameter Decrease

[Naldo6]

The mass of a star is 1.1e31 kg and its angular velocity is 1.40×10-7 rad/s. Find its new angular velocity if the diameter suddenly shrinks to 0.17 times its present size. Assume a uniform mass distribution before and after. [Icm for a solid sphere of uniform density is 2/5 mr^2].

i have to use I1w1=I2w2

it is (2/5)mr^2w1=(2/5)mr^2w2 and find out my w2

but i have all the data unless the r.

what i should put in r?...

 

[Dick]

Don't put anything in for r. Leave it 'r'. If the initial radius is r then the final radius is 0.17*r. The r itself will cancel. If they don't give you a value for a number, it's a pretty sure bet that you don't even need to know it since it will cancel out from both sides of the equation.

 

[baba89]

To calculate the new angular velocity, you will need to find the new radius of the star after its diameter decreases to 0.17 times its present size. This can be calculated by multiplying the original radius by 0.17. Once you have the new radius, you can plug it into the equation (2/5)mr^2w1=(2/5)mr^2w2 and solve for w2. This will give you the new angular velocity after the star's diameter decreases.