Ball in Vertical Circle on End of String, Tangential and Radial Acceleration

[xslc]

Homework Statement

A ball swings in a vertical circle at the end of a rope 1.30 m long. When the ball is 36.1° past the lowest point on its way up, its total acceleration is (-22.5 i + 20.2 j) m/s2.

(a) Determine the magnitude of its radial acceleration.

(b) Determine the speed and velocity of the ball.

Homework Equations

A = v^2/r
Ar = Atotal - Atangential

The Attempt at a Solution

I have no idea where to go with this. I am stuck on the first part. My issue is in figuring out the tangential acceleration so that I can subtract that from the total acceleration to find the radial/centripetal acceleration. My thought is that tangential acceleration should be zero, because the ball is swinging on the end of a string, and its speed should not be changing, only its velocity.

 

[rock.freak667]

You have a=(-22.5 i + 20.2 j) m/s². The acceleration vector is made up of the sum of the radial and tangential acceleration. Using your coordinate system, the j vector points up or towards the center of rotation right? So the radial acceleration is?

 

[xslc]

You have a=(-22.5 i + 20.2 j) m/s². the j vector points up or towards the center of rotation right?

no, up is not towards the center of rotation. it is 36.1 degrees past the bottom