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April 18, 2015

Posted by **Cat** on Tuesday, January 29, 2013 at 8:33pm.

- Physics -
**drwls**, Tuesday, January 29, 2013 at 8:52pmAngular momentum is conserved. That means, in this case,

I1*w1 = I2*w2

where w is the angular velocity and i is the moment of inertia.

The moment of inertia of a solid sphere of uniform density with mass M and radius R1 is

I1 = (2/5)M*R1^2

The moment of inertia of a thin spherical shell of radius R2 is

I2 = (2/3)M*R2^2

The angular velocity w decreases by the ration factor

w2/w1 = I1/I2 = [(2/5)/(2/3)](R1/R2)^2

= (3/5)*(1/3.7)^2 = 0.044

The supernova shell will require 1.5/0.044 = 34 days for a single rotation.

reference:

http://hyperphysics.phy-astr.gsu.edu/hbase/isph.html

- Physics -
**bobpursley**, Tuesday, January 29, 2013 at 8:53pmconservation of momentum

Io wi = If wf

Io for a sphere...mass m, radius R

If for a sphericalshell, massm, radisu 3R

find wf.

http://www.google.com/imgres?imgurl=http://images.tutorvista.com/content/rigid-body/imetia-moments.jpeg&imgrefurl=http://www.tutorvista.com/content/physics/physics-iii/rigid-body/moment-inertia-rod.php&h=408&w=502&sz=46&tbnid=J_WD-nmj-BsktM:&tbnh=90&tbnw=111&zoom=1&usg=__8vA5k1h-LtIQVgw7f4pbYGKNPok=&docid=fk9jd8pjs4ll0M&sa=X&ei=63wIUa2vMOnM2gX21oGoAg&ved=0CDgQ9QEwAQ&dur=5523

- Physics -
**Cat**, Tuesday, January 29, 2013 at 9:15pmWhy is R1 equal to 1?

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