Calculating Radial Acceleration of a Rotating Wheel

[David112234]

Homework Statement

A wheel of diameter 45.0 cm starts from rest and rotates with a constant angular acceleration of 2.50 rad/s2 . At the instant the wheel has completed its second revolution, compute the radial acceleration of a point on the rim in two ways.

1 Using the relationship a_redial=ω²r.

2 From the relationship a_redial=v²/r.

Homework Equations

v=ωr
rotational kinematics
a_redial=ω²r
a_redial=v²/r.

The Attempt at a Solution

α= 2.5
it says second rotation so θ= 2π*2 = 12.57

θ = ωt + ½ α t²
12.57 = ½ 2.5 t²
t= 3.171

ω = ω + α t
ω = 2.5 (3.171)
ω = 7.927

a_redial=ω²r
a = 7.927² * 22.5 = 1413.716694

2 should be the same answer since the equations are equal
why is my answer wrong?

 

[PeroK]

why is my answer wrong?

Is the diameter of the wheel $45m$ or $45cm$?

 

[David112234]

Is the diameter of the wheel $45m$ or $45cm$?

got it, there was my mistake, thank you