Uniform circular motion (centripetal acceleration & force)

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Discussion Overview

The discussion revolves around the concept of uniform circular motion, specifically examining the conditions under which an object experiences centripetal acceleration and force. Participants explore the implications of a proposed motion involving sequential directional changes and whether it can be classified as uniform circular motion.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant describes a scenario where an object changes direction through a series of accelerations and questions if this results in uniform circular motion.
  • Another participant argues that the motion described does not constitute uniform circular motion due to the discontinuous change in direction of force and acceleration.
  • It is noted that while the magnitude of force and acceleration may remain constant, the lack of a smooth, continuous change in direction differentiates it from uniform circular motion.
  • Further clarification is provided that even if the object follows a circular path, the nature of the acceleration in the described scenario does not meet the criteria for uniform circular motion.

Areas of Agreement / Disagreement

Participants generally agree that the described motion does not represent uniform circular motion, but there is a lack of consensus on the implications of the proposed motion and its classification.

Contextual Notes

The discussion highlights the importance of continuous directional change in defining uniform circular motion, as well as the distinction between different types of motion paths, such as parabolic segments versus circular paths.

V0ODO0CH1LD
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Imagine a body moving to the right with velocity v, I then apply a force that accelerates the body leftwards by v and downwards by v.
After one second, the body has stopped moving to the right and is only moving downwards with velocity v.
Then, while I keep accelerating the body to the left until it reaches a velocity v leftwards, I also accelerate the body upwards until it has stopped moving downwards.
By that point, I accelerate the body to the right by v and up by v, after one second it has stopped its movement to the left and is now only moving up.
Finally, I apply a acceleration of v downwards until it stops moving up and rightwards until it reaches a velocity of v to the right.
The object is now exactly in the same point in space it started. And I repeat the same process again and again.

My question is: providing I start the next step at the exact moment I finish the previous one, will the object experience uniform circular motion?
And in that case, clearly those accelerations are less then the centripetal acceleration the body would experience going in the exact same circular fashion. So why is that not a valid centripetal acceleration?
 
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What you've described is not uniform circular motion. The magnitude of the force and acceleration are constant as in uniform circular motion, but their direction changes discontinuously, unlike uniform circular motion.

I haven't worked out the path in detail, but I think it would consist of four parabolic segments, one for each stage of constant force direction; not a circle.
 
jtbell said:
What you've described is not uniform circular motion. The magnitude of the force and acceleration are constant as in uniform circular motion, but their direction changes discontinuously, unlike uniform circular motion.

I haven't worked out the path in detail, but I think it would consist of four parabolic segments, one for each stage of constant force direction; not a circle.

So even if it did go around in the same circular path it wouldn't be considered uniform circular motion because the direction of the force and acceleration doesn't cycle neatly?
 
V0ODO0CH1LD said:
So even if it did go around in the same circular path it wouldn't be considered uniform circular motion because the direction of the force and acceleration doesn't cycle neatly?

Your example does not go in a circular path. As jtbell says, the path will consist of four parabolic segments.

If an object does go in a circular path at a constant speed, then it is by definition in uniform circular motion. In this case, the acceleration of the object will always be towards the centre of the circle, unlike in your example.
 

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