The problem reads, A boy whirls a stone in a horizontal circle, 1.6m above the ground, by means of a string. The radius of the circular motion is 1.0m. The string breaks and the stone hits the ground 5.0m from the point directly below where the string broke. What was the magnitude of the centripetal acceleration of the stone while it was experiencing circular motion, before the string broke? I used the formula a=v^2/r. I started off by trying to find v by using the formula v = squareroot of rg. So v=sqrt(1.0)(9.81). After finding v I used the formula T= 2 pi r/ v. I didn't get the right answer. I've looked through my book, and can't find an example similar to this. I don't know how to use the other info given to me, like knowing the circle was 1.6m above the ground and knowing that it landed 5.0m away.