- #1
Saitama
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Homework Statement
A thin rod of length L and mass m is suspended freely from one end. It is pulled to one side and then allowed to swing like a pendulum, passing through its lowest position with angular speed ω. In terms of these symbols and g, and neglecting friction and air resistance, find the rod's kinetic energy at it's lowest position.
Homework Equations
The Attempt at a Solution
I am a poor guy in rotational dynamics, please bare with me.
[tex]KE=\frac{1}{2}Iω^2+\frac{1}{2}Mv^2[/tex]
If i use this formula i get the wrong answer. The answer is [itex]\frac{ML^2ω^2}{6}[/itex].
If i use [tex]KE=\frac{1}{2}Iω^2[/tex], i get the right answer but i don't understand why is this correct? Why i can't use the first formula? Any explanation would be very helpful.
Thanks!