Acceleration at constant velocity?

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SUMMARY

The discussion centers on calculating the torque required to maintain a constant speed along a cardioid path. The relevant equations include torque defined as t = r x f and the acceleration formula a = (r_dot dot - r*Θ_dot ^2) r_hat + (r*Θ_dot dot + 2 r_dot * theta_dot) theta_hat. A key conclusion is that maintaining constant speed involves not just the magnitude of velocity but also its direction, indicating that changes in direction constitute acceleration.

PREREQUISITES
  • Understanding of torque and its calculation using the cross product.
  • Familiarity with polar coordinates and their application in motion analysis.
  • Knowledge of vector quantities, specifically velocity and acceleration.
  • Basic grasp of calculus, particularly derivatives as they apply to motion.
NEXT STEPS
  • Study the principles of torque in rotational dynamics using "Classical Mechanics" by David Morin.
  • Learn about polar coordinate transformations and their applications in physics.
  • Explore vector calculus, focusing on derivatives and their physical interpretations.
  • Investigate the concept of centripetal acceleration and its relation to circular motion.
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in understanding the dynamics of motion in non-linear paths, particularly in the context of rotational mechanics.

ma18
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Homework Statement



Calculate the torque, t about origin that must be applied to a particle for it to maintain a constant speed v along a cardiod.

Homework Equations



t = r x f

a = (r_dot dot - r*Θ_dot ^2) r_hat + (r*Θ_dot dot + 2 r_dot * theta_dot) theta_hat

The Attempt at a Solution



Constant speed means that the derivative of the speed wrt time = 0 = magnitude of the acceleration. But then if the mag of the acceleration is zero then everything turns to zero because it is all related. So I'm guess there is something else which constant speed implies and I am wrong. What is it?
 
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ma18 said:

Homework Statement



Calculate the torque, t about origin that must be applied to a particle for it to maintain a constant speed v along a cardiod.

Homework Equations



t = r x f

a = (r_dot dot - r*Θ_dot ^2) r_hat + (r*Θ_dot dot + 2 r_dot * theta_dot) theta_hat

The Attempt at a Solution



Constant speed means that the derivative of the speed wrt time = 0 = magnitude of the acceleration. But then if the mag of the acceleration is zero then everything turns to zero because it is all related. So I'm guess there is something else which constant speed implies and I am wrong. What is it?
Velocity is a vector quantity, so, if the direction of the velocity vector changes, that constitutes acceleration also. It's not only the speed that counts, it's also the direction.

Chet
 

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