Angular Kinematics: Calculating Wheel Rotation in 5s

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SUMMARY

The discussion centers on calculating the angular displacement of a wheel with an initial angular velocity of 20 rad/s that accelerates to 40 rad/s over a 5-second interval. The user correctly applies the formula for angular acceleration, determining an angular acceleration of 4 rad/s². Using the kinematic equation, they calculate the angular displacement (theta) to be 150 radians. Despite their calculations being accurate, the user questions the validity of the provided answer choices, suggesting a possible error in the source material.

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A wheel rotates about a fixed axis. Initial angular velocity of 20 rad/s.
During a 5 s interval the ang. velocity increases to 40 rad/s. (const angular acceleration) How many radians does the wheel turn in 5 s?

Having a bit of trouble, not quite sure why...
so I start out with
w = w0 + at
40 = 20 + a*5
a = 4

w^2 = w0^2 + 2*4*theta
theta = 150 radians

I thought that was the correct answer, however, that's not one of the choices. Anyone see what I'm doing wrong?
 
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I also have 150 radians... Are you sure you wrote the question word for word, or maybe there is an answer in degrees or something? It's also possible the book/test/homework/quiz/whatever it is, is wrong.
 
I second the 150 radians.
 

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