- #1
SothSogi
- 20
- 4
Homework Statement
(Sorry for not typing like Latex, I still do not know how)
One has a uniform stick of length l which is held horizontally. At t=0 it is released from rest. At the same time, a sharp upward blow by a force of magnitude F perpendicular to the stick is applied at a distance d for some \delta t. The stick flies then fall under the action of gravity. One has to determine the distance d such that when the stick's center falls back to the same height it started with, the stick rotated exactly once. (Assume F is much larger than gravity when the impulse was delivered) (I guess I can use Delta t in my answer, therefore I do not worry about it)
Homework Equations
torque=r x F
L=I*omega (I is the moment of inertia)
omega=dtheta/dt
The Attempt at a Solution
I got
torque=d*F*Delta t=Delta L
Since at the beginning only F delivered angular impulse, and it was at rest, I have
torque=d*F*Delta t=L_f=I*omega
Now, one revolution implies dtheta=2*pi. So I have
d*F*Delta t=I*[(2*pi)/dt]
But I do not know what to do with that dt.
Any suggestions?
Thanks in advance.