What is instantaneous acceleration?

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Discussion Overview

The discussion revolves around the concept of instantaneous acceleration, exploring its definition, implications, and the logical challenges associated with it. Participants engage in a technical examination of how instantaneous acceleration can be understood within the framework of calculus, particularly in relation to velocity and time. The conversation includes both theoretical and conceptual aspects, with references to mathematical definitions and practical examples.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants question the validity of instantaneous acceleration, arguing that it seems illogical to have a change in velocity at a specific instant.
  • Others assert that acceleration is defined as the derivative of velocity with respect to time, suggesting that this definition allows for instantaneous acceleration when considering limits as time approaches zero.
  • A participant proposes that instantaneous acceleration is useful for determining the direction and magnitude of velocity changes, emphasizing its vector nature.
  • Concerns are raised about the practicality of measuring instantaneous acceleration and velocity, with some participants suggesting that while definitions may be mathematically sound, they may not align with physical intuition.
  • Several participants reiterate that both instantaneous velocity and acceleration can be understood as derivatives, but there is contention over the interpretation of what it means to have a change at an instant.
  • Some participants provide examples, such as the acceleration of a car, to illustrate how instantaneous acceleration can vary over time, contrasting it with average acceleration.

Areas of Agreement / Disagreement

Participants express differing views on the logical consistency of defining instantaneous acceleration. While some agree on the mathematical framework, others remain unconvinced about its physical interpretation, leading to an unresolved debate on the topic.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the definitions of velocity and acceleration, as well as the dependence on calculus concepts. The conversation reflects a range of interpretations and applications of these definitions without reaching a consensus.

  • #31
A.T. said:
Right, so if you understand instantaneous velocity, then what is your problem with Instantaneous acceleration? Both are derivatives w.r.t time.We cannot help you, if you just keep repeating "How can it be..." without explaining what your problem with it is.
I just edited my post
 
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  • #32
parshyaa said:
Suppose i am applying force continuously on an object, then object accelerates, and then somebudy asked what is the acceleration of that object when time was 4 second
a = F / m
 
  • #33
A.T. said:
a = F / m
Yes but i just gave that example to explain the importance of instantaneous acceleration, finally acceleration is the ratio of velocity w.r.t time , therefore it can occur at a particular instant of time.
 
  • #34
parshyaa said:
Yes but i just gave that example to explain the importance of instantaneous acceleration,
Then you should add that the force or mass varies with time. Otherwise instantaneous acceleration equals average acceleration.
 
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  • #35
A.T. said:
Then you should add that the force or mass varies with time. Otherwise instantaneous acceleration equals average acceleration.
Yes, i meant the same.
 
  • #36
parshyaa said:
finally acceleration is the ratio of velocity w.r.t time
Acceleration is the derivative of velocity wrt time.

parshyaa said:
therefore it can occur at a particular instant of time
It sounds like you now agree that instantaneous acceleration is meaningful, just like instantaneous velocity.
 
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  • #37
parshyaa said:
Instantaneous velocity: its the velocity of an object at a particular instant/moment of time.
mathematically: Its the rate of change of displacement/position of an object w.r.t time.
Instantaneous acceleration: its the acceleration of an object at a particular instant/moment of time.
Mathematically: its the rate of change of velocity w.r.t time.
Suppose i am applying force continuously on an object, then object accelerates, and then somebudy asked what is the acceleration of that object when time was 4 second, therefore introduction of instantaneous acceleration is must.
Thank you
@Dale
 
  • #38
parshyaa said:
You didn't ask any questions, but all of those statements look fine.
 
  • #39
russ_watters said:
You didn't ask any questions, but all of those statements look fine.
Yes,because my doubt is clear now, thanks to all of you
 
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  • #40
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  • #41
rumborak said:
On a related side note, there is something called "jerk" in physics, which is the derivative of the acceleration over time:

https://en.m.wikipedia.org/wiki/Jerk_(physics)
And the jerk is what actually happens in pretty well every mechanical occurrence . Put your foot down on a car accelerator and you will find the force on your back varies with time. (Like when the turbo kicks in. You can't use the SUVAT equations with motor cars because the acceleration is not uniform at all.
Edit: When I first was taught SUVAT in School, I missed the word "uniform" in "uniform acceleration'. That looking out of the window incident accounted for a lot of initial problems with comprehension. I wish I had learned that lesson because I have been nodding off regularly at vital moments ever since. :rolleyes:
 
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  • #42
like a lot of people out there that paradoxical thing bugged me since high school, but no one ever seemed to explain me better than this guy:



OP I strongly advise you to watch this video to really get a clear(er) picture of a derivative.
 
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  • #43
The video posted by LLT71 is interesting, " Instantaneous rate of change" is explained clearly in that. Simply it is the rate of change occurs during a very small duration of time, when we take the derivative we allow the time difference to approach zero,
 
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  • #44
Vidujith Vithanage said:
The video posted by LLT71 is interesting, " Instantaneous rate of change" is explained clearly in that. Simply it is the rate of change occurs during a very small duration of time, when we take the derivative we allow the time difference to approach zero,
He deals with the apparent problem quite well but he doesn't really needs go to all that trouble. If you are prepared to use Maths as the primary way of explaining this sort of process and only use hand waving as a secondary medium, there never would be a problem. This is all down to Mathsphobia, imo.
 
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