# Homework Help: Tangential and radial components of acceleration - answer seems odd

1. Oct 27, 2008

### Vanessa23

1. The problem statement, all variables and given/known data
A 60 cm diameter wheel accelerates uniformly about its center from 120 rpm to 300 rpm in 5s.
1) Determine its angular acceleration.
2) Determine the radial component of the linear acceleration of a point on the edge of the wheel 2s after it has started accelerating.
3)Determine the tangential component of the linear acceleration of a point on the edge of the wheel 2s after it has started accelerating.

2. Relevant equations
1) alpha=w2-w1/delta(t)
2 and 3) w'=w+alpha t'
v=Rw'
tangential component =alpha r

3. The attempt at a solution
1) I determined that alpha = 3.77rad/s^2
2)w'=120*2pi/60 + 3.77*2s
w'=20
v=.6/2*20 = 6
radial = 6^2/.3 = 120 m/s^2
this seems very high!! shouldn't it be less than 3.77?

3) tangential = 3.77*.3 = 1.131 m/s^2

2. Oct 27, 2008

### Redbelly98

Staff Emeritus
Your numbers look right to me. There's no reason or sense in comparing a_radial to alpha when they don't even have the same units. I.e., 120 m/s^2 is neither less than, equal to, or greater than 3.77 rad/s^2.

EDIT:
Looks like you wrote w' when you probably meant w (or ω), the rotation rate in rad/s.