- #1
TheCanadian
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Homework Statement
A uniform rod of length b and mass m stands vertically upright on a floor and then tips over.
a) Assuming that the floor is rough (i.e., the end of the rod that is initially touching the floor cannot slip), what is the rod’s angular velocity when it hits the floor?
2. Homework Equations
$$ T = \frac{1}{2} mv^2 + \frac{1}{2}I\omega^2 $$
The Attempt at a Solution
I have found the solution, but only by setting $$ U_i = T_f $$ (initial potential energy = final kinetic energy). But what I found odd is that I set $$ T_f = \frac{1}{2}I\omega_f^2 $$ and stated the translational energy term goes to 0. I got the right answer by doing this, but it doesn't seem right. I understand that the CoM of the rod remains at the same length radially, but since there is an x- and y-component to its velocity, shouldn't it have a non-zero final translational velocity? Although this is reminiscent almost of a ball kept stationary but rotated, which has only rotational energy, and zero net translational energy (at its CoM)...but are these two cases really analogous? In one case it seems very clear that the CoM is moving, while in the other, the CoM is stationary from a fixed axis.