 #1
simphys
 298
 43
 Homework Statement:

The 0.75kg smooth can is guided along the circular
path using the arm guide. If the arm has an angular velocity ##\theta^. = 2rad/s## and an angular acceleartion of 0.4 rad/s^2 at the instant ##\theta = 30degrees##, determine the force of the guide on the can. Motion occurs in the horizontal plane.
 Relevant Equations:
 cylindrical stuff
so I was wondering. there is this normal force on the can from the path. And there's this formula to find the angle between the radial line and the tangent or also between the normal force and either the radial or theta axis. the formula is ##\psi = r/dr/d\theta##. The thing is that here they have just used ##\theta = 30degrees## for some reason and I can't quite see why they use 30 degrees as being the angle between the axis and the normal force instead of the psi angle. Could someone clarify this please?
Thanks in advance.