# How would I go about computing the radial acceleration when given i and j components?

1. Oct 18, 2012

### samatar

1. The problem statement, all variables and given/known data
I attempted this problem, and i have a midterm tommorow. I thought my approach was correct but I don't have a clue if it actually is. I drew a simple right angle triangle according to the information given in the question.

A ball swings in a vertical circle at the end of a rope 1.40 m long. When the ball is 36.1° past the lowest point on its way up, its total acceleration is (−22.5i + 20.2j ) m/s^2. For that instant, do the following. Find the radial acceleration. Also compute the velocity at this acceleration

2. Relevant equations

l a l = √(ai^2 + aj^2) , ar=v^2/r

3. The attempt at a solution

l a l= √(-22.5)^2+(20.2)^2=30.24

ar=30.24cos36.1

v=√(30cos36.1)(1.4) = 5.8

Last edited: Oct 18, 2012
2. Oct 18, 2012

### tiny-tim

welcome to pf!

hi samatar! welcome to pf!

no, the radial component of acceleration will be the total acceleration "dot" the unit vector in the radial direction

try again