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January 25, 2015

January 25, 2015

Posted by **Goldberg** on Saturday, May 5, 2012 at 9:07pm.

- Physics 121 -
**Goldberg**, Saturday, May 5, 2012 at 9:08pmPlease show the formula and how you do it. Thx

- Physics 121 -
**bobpursley**, Saturday, May 5, 2012 at 9:13pmLook at energy:

potential energy lost= kinetic energy gained

mgh=1/2 m vf^2 +1/2 I w^2

mgh=1/2 m vf^2 + 1/2 I (vf/r)^2

Now, you have to decide the moment of inertia for the cylinder. Solid, or not. Lets just assume it is hollow for this demonstration.

I= m r^2

then

mgh= 1/2 m vf^2+1/2 m vf^2

Now, average velocity going down was Vf/2, so in three seconds it went 1.5Vf

h= 1.5Vf

1.5 mg Vf= 1/2 m Vf^2+ 1/2 m Vf^2

you can solve for Vf.

I would divide by mVf, and solve

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