What is instantaneous acceleration?

Join the discussion
Ask a follow-up here, or get your own question answered by working scientists, mathematicians and engineers — people, not an autocomplete.
Real named experts · corrections over time · the nuance an AI answer skips
43 replies · 9K views
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
 
Physics news on Phys.org
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
 
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.
 
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.
 
  • Like
Likes   Reactions: parshyaa
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.
 
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.
 
  • Like
Likes   Reactions: parshyaa
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
 
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
 
  • Like
Likes   Reactions: russ_watters and Dale
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:
 
Last edited:
  • Like
Likes   Reactions: parshyaa
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.
 
  • Like
Likes   Reactions: parshyaa and sophiecentaur
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,
 
  • Like
Likes   Reactions: LLT71
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.
 
  • Like
Likes   Reactions: Vidujith Vithanage and parshyaa