A rod of mass 4.3 kg and length 4.3 m hangs from a hinge as shown in Figure P9.28. The end of the rod is then given a “kick” so that it is moving at a speed of 2.3 m/s. How high will the rod swing? Express your answer in terms of the angle (in degree) that the rod makes with the vertical.
Hinge --> 0
i <-- Steel rod
-------> swings this way
w=2.3/4.3= 1 rad per second.
Now, the moment of Inertia for the rod swinging about an end is... 1/3 ml^2
initial KE= 1/2 I w^2=1/6 ml^2 figure all that out given m, l
now, final PE= mgh were h is to the center of mass. Drawing the figure, then
finally we have
costheta= 1- 4.3/6g
theta= arc cos ( above)
check all this.posted by bobpursley