# Tangential and radial acceleration

1. Sep 5, 2009

### MechaMZ

1. The problem statement, all variables and given/known data
A ball swings in a vertical circle at the end of a rope 1.50 m long. When the ball is 37.5° past the lowest point on its way up, its total acceleration is (-22.5 i + 20.2 j) m/s2.

3. The attempt at a solution
Determine the magnitude of its radial acceleration.

My attempt, but wrong answer.
1. total acceleration = 30.237, by resolving (-22.5 i + 20.2 j) m/s2 into R
2. build a geometry triangle, to calculate ar
30.237sin 37.5 = ar
1. The problem statement, all variables and given/known data

I think the ans should about 27-29m/s2

2. Relevant equations

3. The attempt at a solution

2. Sep 5, 2009

### Staff: Mentor

You found the magnitude of the total acceleration, but what about its direction?

Hint: Try working with each component of the total acceleration. How much of each component is in the radial direction?

3. Sep 5, 2009

### MechaMZ

I think I understand now, there shouldn't have any tangential acceleration for this uniform circular motion. so the R is the ac.

Thank you Doc Al