Magnitude of Acceleration on Merry-Go-Round

[teresalin2004]

Homework Statement

At a playground you let your kid sister (30 kg) kneel on the surface (near the edge) of a 2.1 meter diameter merry-go-round. You push the merry-go-round so that it constantly accelerates from rest to a final speed of 1.7 rotations per second at the end of a 25 second interval. (please complete all questions using radians)
After it comes up to speed, you stop pushing and the merry-go-round continues to run at a constant rate of 1.7 rotations per second. What is the magnitude of your sister's acceleration, if any?

Homework Equations

V is the tangental velocity in m/s
r is radius of circle in meters
ω is angular velocity in radians/sec
a is in m/s²
[/B]
1.7 rotations per second x 2π rad/rev = 10.68 rad/s
ang. acc. = Δω/Δt = 10.68/25 = 0.427 rad/s²
134 rad x 1 rev/2πrad = 21.25 rev

The Attempt at a Solution

I got the first part of the question right, but I have no idea what I am doing wrong for the last part shown above. This is what I did:

a = rω² = (2.1)(10.68)² = 240 m/s²
[/B]

 

[Bandersnatch]

Diameter =/= radius!

 

[tms]

in the first place, 2.1 meters is the diameter, and you have to use the radius. In the second place, as far as I can see there is only one question.