Calculating Rotational Acceleration of a Wheel

[kfish]

Homework Statement

A rotating wheel requires 3.05 s to rotate through 37.0 revolutions. Its angular speed at the end of the 3.05 s interval is 97.1 rad/s. What is the constant angular acceleration of the wheel?

Homework Equations

Well from basic calculus I know that acceleration is equal to (dV/dT) or the derivative of velocity over derivative of time.

That is the only pertinent equation I can think of for this problem.

The Attempt at a Solution

I used the velocity, 97.1 rad/s, and divided it by the time, 3.05s.

(97.1/3.05)= 31.84 rad/s^2

According to the online homework this is incorrect. I cannot think of any other way to calculate it since the radius is not given.

Homework Statement

A racing car travels on a circular track of radius 230 m. Suppose the car moves with a constant linear speed of 53.0 m/s.

(b) Find the magnitude and direction of its acceleration.

Part (a) had me calculate the velocity which came out to 0.23 rad/s. The velocity is correct.

Homework Equations

a= linear acceleration
A=rotational acceleration
R=radius

A=a/R

circumference = 2piR

The Attempt at a Solution

I figured since it says a constant linear acceleration then the angular acceleration=0 because A=(0)/(230) = 0. This answer is incorrect according to the online homework. I'm not sure what else to do.

 

[Kurdt]

The following page from hyperphysics may be of use to you.

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html