Student spinning with textbook at different distances

[primeboss]

Homework Statement

A student hold a 2.0 kg textbook to their chest as they spin at an angular velocity of 6 rad/sec. Assuming the mass moment of inertia of the student to be 1.4 kgm^2, what is the angular velocity if the student hold the book 0.7 meters away

Homework Equations

The Attempt at a Solution

I do not know where to start. i can find a correlation with angular velocity and moment of inertia. Also do i use energy?

 

[tiny-tim]

welcome to pf!

hi primeboss! welcome to pf!

momentum and angular momentum are always conserved

 

[primeboss]

Thanks for the reply, but i am still confused into how to approach the problem

 

[tiny-tim]

uhh? use conservation of angular momentum …

what do you get?​

 

[primeboss]

"I don't see how i can find the intial momentum of inertia, since i do not know the radius but only the mass"

edit:NEVERMIND i got it. Thanks for all your help.