What is the magnitude of the Reaction Force?

[jj8890]

Homework Statement

In my homework we are asked to find the magnitude of the reaction force at the pivot at a instant and earlier in the problem we found the magnitude of the angular speed at one instant, the magnitude of the angular acceleration at the same instant, and the magnitude of the acceleration of its center of mass at the same instant. I have attached the diagram but basically I am not sure exactly what the magnitude of the reaction force is, we haven't talked about it in class. Could someone clarify this for me?

 

[Doc Al]

At any given instant, the pivot exerts some force on the rod. That's what they are calling the "reaction" force. Figure it out using Newton's 2nd law.