Does tangential acceleration have direction like regular acceleration?

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Discussion Overview

The discussion revolves around the nature of tangential acceleration in relation to angular acceleration and torque, particularly in the context of a spinning wheel. Participants explore concepts of acceleration, torque, and the effects of forces on rotational motion, with a focus on theoretical implications in both static and dynamic scenarios.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that applying a force perpendicular to the radius of a wheel generates torque and changes angular acceleration, raising questions about the existence of torque when no forces act on a spinning wheel.
  • Another participant asserts that without an acting force, there can be no torque or angular acceleration, regardless of the wheel's state.
  • A participant expresses confusion between linear and angular acceleration, stating that a spinning wheel has centripetal and tangential acceleration but not angular acceleration if there is no change in angular velocity.
  • One participant clarifies that different points on a spinning wheel experience varying centripetal accelerations, and the center has none.
  • A participant discusses the concept of torque, emphasizing that it can be applied about any point, not just the center of mass, and introduces the idea of a force couple to explain torque intuitively.
  • Another participant reiterates that a spinning object with uniform angular velocity does not have tangential acceleration unless torque is applied, highlighting the confusion surrounding the definitions of acceleration and tangential velocity.
  • One participant notes the distinction between tangential acceleration and regular acceleration, pointing out that tangential velocity does not include direction, which adds to the confusion in terminology.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between torque, angular acceleration, and tangential acceleration, with no consensus reached on the implications of these concepts in the absence of external forces.

Contextual Notes

Participants acknowledge the complexity of the definitions and relationships between linear and angular quantities, as well as the potential for confusion in terminology, particularly regarding tangential acceleration and velocity.

localrob
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I know if I apply a force(perpendicular to he radius) to a wheel to rotate it, I am applying a torque. I change the wheel's angular acceleration, thus creating a torque.
I can find the direction of a torque via the right hand rule.

If there is a wheel spinning in space where there are no forces acting on it, does the wheel still have a torque?
([tex]\tau[/tex] = L[tex]\alpha[/tex])
Doesn't the wheel still have an angular acceleration?

I'm afraid I've been thinking about all of this too much and am beginning to confuse myself.
 
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In space or not, if there is no force acting on a wheel, there is no torque and no angular acceleration.
 
ok, I think I was getting the linear acceleration and angular acceleration confused.

A spinning wheel will have centripetal and tangential acceleration, but it will not have angular acceleration b/c there is no change in angular velocity.

So not all spinning objects have angular acceleration or torque.
 
Correct, with the caveat that I wouldn't say "the wheel" has a centripetal acceleration - different points on the wheel will have different centripetal acceleration and a point at the center will have none.
 
Push on the center of mass of an object with a force, and you've applied torque. Doesn't sound as if it makes sense does it?

Torque is defined as a force acting about a point. You can choose any point you like. It doesn't have to be the center of mass. If the force is one pound, and the point of interest is one foot from the line of force, the torque is one foot-pound.

Take a wheel that is at rest and not spinning. If you push on the rim, it will both spin and obtain a translational velocity. If you don't want it to give it a velocity, you apply an equal and opposite force on the opposite side of the rim. This is called a Force Couple. It's the intuitive idea a lot of use have about what is torque, before we lean the weird definition.
 
localrob said:
A spinning wheel will have centripetal and tangential acceleration, but it will not have angular acceleration b/c there is no change in angular velocity.
You're almost right. No point of an object spinning with uniform angular velocity has tangential acceleration. Only if you apply a torque, does tangential acceleration arise.
 
sganesh88 said:
You're almost right. No point of an object spinning with uniform angular velocity has tangential acceleration. Only if you apply a torque, does tangential acceleration arise.

True, but you have to admit, it is confusing. Acceleration is the change in velocity over time, and tangential acceleration is the change in tangential velocity over time, but tangential velocity doesn't include direction like regular acceleration does. It's just speed.

So, many thanks to the jerk who decided against calling it tangential speed.
 

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