For Doc, rates of change of acceleration

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    Acceleration Change
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Discussion Overview

The discussion revolves around the units for rates of change of acceleration, specifically addressing the concept of "jerk" and how it can be expressed in different units. Participants explore the relationship between acceleration measured in "g" and its rate of change, as well as the implications for calculations in various contexts.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions how acceleration ("a") and its change ("Δa") can have the same units of "g," suggesting that the rate of change of acceleration should be in "g/s."
  • Another participant asserts that the rate of change of acceleration, or jerk, has units of m/s³, clarifying that the change in acceleration can be expressed in terms of "g."
  • A participant discusses the need to express the rate of change of acceleration in m/s³ for a specific project, indicating a method for converting measurements from "g" to m/s² and then to m/s³.
  • There is a suggestion that jerk can also be expressed as g/s, prompting further inquiry into unit conversions.
  • One participant reflects on their understanding of the units involved, noting that the change in acceleration over a measurement period must be in "g," while also expressing a need to convert to m/s³ for future calculations.

Areas of Agreement / Disagreement

Participants express differing views on the appropriate units for rates of change of acceleration, with some agreeing on the definitions while others seek clarification on conversions and implications for their specific contexts. The discussion remains unresolved regarding the best approach to unit conversion and the interpretation of "g" in these calculations.

Contextual Notes

Participants highlight the importance of distinguishing between change and rate of change, as well as the potential confusion arising from different measurement methods. There are references to specific measurement periods and the need for conversions that may not be universally applicable.

Who May Find This Useful

This discussion may be useful for individuals interested in the technical aspects of measuring rates of change in acceleration, particularly in contexts involving different unit systems and conversions in physics or engineering applications.

Micky
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Sometime ago you very kindly advised me regarding units for rates of change of acceleration.

I still don't fully understand how "a" and "Δa" can have the same units, "g". If acceleration is measured in terms of "g", shouldn't the rate of change of acceleration be measured in terms of g/s?

Thanks.
 
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You are correct.

rate of change of acceleration, also called jerk, has units

[tex]\frac m {s^3}[/tex]
 
Originally posted by Micky
Sometime ago you very kindly advised me regarding units for rates of change of acceleration.
As Integral states, the rate of change of acceleration is called "jerk".
I still don't fully understand how "a" and "Δa" can have the same units, "g". If acceleration is measured in terms of "g", shouldn't the rate of change of acceleration be measured in terms of g/s?
You are confusing change with rate of change. The units of a change in any quantity will be the same units as the quantity.

Example: Your weight goes from 165 lbs to 170 lbs. The change is 5 lbs, same units as your weight.

If the change took place over 1 month, the (average) rate of change of your weight would be: 5 lbs/month. Different quantity, different units.

Similary, the CHANGE of acceleration will have units of m/s2 (you can measure in terms of "g" if you want), but the RATE of change of acceleration would be in units of m/s3 (you can use g/sec, if you dare).

Bottom line: Change is Δa; rate of change is Δa/Δt.
 
Thanks Integral, can jerk also be expressed as g/s?
 
I've had another look at the original thread here

I think I see now how Doc's answer is correct for my method of measuring rates of change of acceleration. I'm comparing two consecutive measurements of acceleration (units = "g"), therefore the answer = change in acceleration over the time period and must be in "g" .. I think. This is fine for the current project which is comparing rates of change of accel.

However, at some stage I will need to express the rate of change of acceleration in units of m/s/s/s. So if the measurement period is, say, 0.01s then I need to multiply the change in acceleration over this period by 100.

I suspect that the calculation should be {measured accel value in units of g}*9.8*100 which should then give me the rate of change of acceleration measured in m/s/s/s ??

Is there a thread with info about inserting symbols into posts?
 
Originally posted by Micky
I've had another look at the original thread here

I think I see now how Doc's answer is correct for my method of measuring rates of change of acceleration. I'm comparing two consecutive measurements of acceleration (units = "g"), therefore the answer = change in acceleration over the time period and must be in "g" .. I think. This is fine for the current project which is comparing rates of change of accel.

However, at some stage I will need to express the rate of change of acceleration in units of m/s/s/s. So if the measurement period is, say, 0.01s then I need to multiply the change in acceleration over this period by 100.

I suspect that the calculation should be {measured accel value in units of g}*9.8*100 which should then give me the rate of change of acceleration measured in m/s/s/s ??

Is there a thread with info about inserting symbols into posts?
the LaTeX thread.
 

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