As you've got omega first I think you've covered yourself whatever.

Bob

]]>as v = rw. But, this question still confuses me... are they asking for the ANGULAR velocity w, or just the instantaneous velocity of the end of the rod? In which case, with r = l;

v = rw, using my w from post #1;

]]>I suppose you could find a way of calculating the KE directly. Write the velocity in terms of omega and l.

Maybe try it.

B

]]>EDIT just read what you have asked. thinking ..........

Moments of inertia can be calculated by integration. It's ages since I did this so there's lots of cobwebs to blow away first.

I'm sure you could do it.

MI of whole = integral over length of rod (MI of a dx segment)

Bob

]]>Is there a way to do this without knowing anything about moments of inertia? This question is taken from an admissions test in 2007 from Trinity College, Cambridge, but most applicants typically will not have covered this until Year 13 (it's an M5 topic)... can it be done with only M1-M3 knowledge?

]]>That looks good to me.

http://en.wikipedia.org/wiki/List_of_moments_of_inertia

Bob

]]>It looks like the mass does cancel out, after all.

Just one more thing-Why are you using l/2 in tbe I_z formula if the rotation is around the end of the rod?

]]>One end of a rod is attached to the ceiling in such a way that the rod can swing about freely. The other end of the rod is held still so that it touches the ceiling as well. Then, the second end is released.

I don't see how else this could be interpreted... clearly the starting position is the rod in its horizontal position.

= (left end fixed)

goes to

|| (top end fixed)

]]>