period of the sun

[wildrjetta]

Could someone help me start this problem. My mind it in the angular momentum mode and I am having trouble seeing where to start on this one. :confused:

The sun's radius is 6.96E8m and it rotates with a period of 25.3d. Estimate the new period of rotation of the sun if it collapses with no loss of mass to become a neutron star of radius 5.5km. Give the result in seconds.

Thank you very much!

[CartoonKid]

With the given radius you can find I_{initial} and I_{final}. With the given period, find out \omega_{initial}. Then you use conservation of angular momentum to achieve your answer.

[Phymath]

as such...(you don't need the moments of inertia exactly because it maintains a spherical shape and same mass so those factor out)

(r_i)^2 \omega_i = (r_f)^2 \omega_f
\omega_f = \frac{(r_i)^2 \omega_i}{(r_f)^2}
T_{new} = \frac{2 \pi}{\omega_f}

follow complete done

[wildrjetta]

I calculated two different answers, both of which were to my dismay incorrect....but I am thinking that a conversion error might be the culprit. I am having trouble understanding what "a period of 25.3d" is -- as in, what does "d" stand for....should it be a time unit?

[cougar_21]

in a period d=days

[wildrjetta]

THANK YOU THANK YOU THANK YOU!!! to everyone involved in helping with this problem!! :biggrin: