What is the formula for finding centripital acceleration in a spinning disc?

[ttttrigg3r]

Homework Statement

There is a spinning disc. Object A sits R distance from center and object B sits R/2 distance away. V_B=piR/T and V_A=2piR/T

Homework Equations

Find the magnitude of the acceleration of object B. Assume that the cylinder makes one complete turn in a period of time .

The Attempt at a Solution

The answer is a=(2pi²R)/T² .


From using centripetal acceleration=v²/R , i got
a_c=pi²R/T²

There is a coefficient of 2 that I am missing in my answer from the correct solution, but I have double checked. Am I using the wrong formula here? where did the 2 come from in the answer?

 

[ttttrigg3r]

NVM. spent an hour on it and finally got it. Supposed to divide by R/2 not R