# Angular Acceleration (p.22)

1. Oct 25, 2014

### gcombina

1. The problem statement, all variables and given/known data
Which statement concerning a wheel undergoing rolling motion is true?

(a) The angular acceleration of the wheel must be zero m/s2.

(b) The tangential velocity is the same for all points on the wheel.

(c) The linear velocity for all points on the rim of the wheel is non-zero.

(d) The tangential velocity is the same for all points on the rim of the wheel.

(e) There is no slipping at the point where the wheel touches the surface on which it is rolling

2. Relevant equations

3. The attempt at a solution

(a) Angular Acceleration

∝ = Δω/τ

I am confused on this first option, if the wheel is rolling, does it mean that there is a force pushing this wheel? (since there is friction), therefore IT IS accelerating.

Am I approaching this option correctly?

2. Oct 25, 2014

### haruspex

No.

3. Oct 25, 2014

### gcombina

so why is the wheel rolling? if there is air friction and the road friction?

4. Oct 26, 2014

### haruspex

The short answer is, we don't know and we don't care why it is rolling. There are many possible reasons, and they don't all imply it's getting faster.
Which of the following would qualify as "a wheel undergoing rolling motion"?
• a disc rolling freely down a ramp, accelerating
• a disc which has rolled down a dip, but is now rolling freely up the other side
• a car wheel, the car driving at constant speed