Rotational Motion angular speed

[physgrl]

Homework Statement

11. A wheel with an angular speed of 2.0 rad/s is rolling on a horizontal surface and starts down a ramp. It rolls down the ramp with a constant angular acceleration of 2.5 rad/s2. If it takes 8 s to reach the bottom of the ramp, what is the final angular speed of the wheel at the bottom?

a. 20 rad

*b. 22 rad/s

c. 18 rad/s

d. 25.5 rad/s

Homework Equations

a_centripetal=Δω/t

The Attempt at a Solution

I plugged into the equation initial velocity as 2.0rad acceleration as 2.5 and time as 8 and solved for final velocity which have me 20 rad/s the answer key says its 22

 

[LawrenceC]

The final angular speed consists of the initial angular speed plus the amount it accelerated on the ramp.

Pertinent equation is: omega final = omega initial + alpha *time

 

[physgrl]

Ohh i did my math wrong sory