Angular Acceleration (p.22)

[gcombina]

Homework Statement

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

Homework Equations

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?

 

[haruspex]

if the wheel is rolling, does it mean that there is a force pushing this wheel?

No.

 

[gcombina]

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

 

[haruspex]

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

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

 

[HalfLostAndSearching]

You are correct in thinking that there is a force pushing the wheel (friction) and therefore it is accelerating. However, angular acceleration refers to the change in angular velocity, not linear acceleration. In this case, the angular velocity of the wheel is constant, so the angular acceleration would be zero. Option (a) is correct.