What Is the Correct Method to Calculate W and Alpha in Planar Kinematics?

[smruthi92]

pls see attached file.

so i thought i could use this eqn:

a_A = w² AO e_n + alpha AO e_t

but when i try to work out w, something goes wrong. i do:

w = 7.16605 (normal velocity i found by having the given velocity as a y coordinate one, then resolving for normal/tangential) / 0.25. but this itself is wrong. what have i done? also how do i calculate alpha? i have no IDEA how to do it!

thanks a lot for ur help,
cheers,
s.

 

[omoplata]

alpha is the angular acceleration, or the rate of change of w w.r.t. time.

Tell me if you get stuck.

 

[smruthi92]

yeh but how do i calculate it with the data given? we haven't been given an equation to differentiate to find alpha. also I am still stuck on calculating w.

 

[omoplata]

w is the angular velocity, or the rate of change of theta w.r.t time.

If you find w as a function of theta you can differentiate w.r.t time.

You can find w as a function of theta by considering the component of the linear velocity of the pin which is perpendicular to AO.