Rate of change of acceleration - basic

In summary: What is it that you are measuring the Δa of? How are you making the measurements?I'm measuring the acceleration of a body in the vertical direction using an accelerometer and datalogger. The raw data is downloaded to a laptop and saved as a text file. The data is presented in two columns, time (measured in units of 0.01s) and acceleration (measured as g). So this means that at any given point in time I know the acceleration of the body.
  • #1
Micky
9
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I'm plotting rate of change of acceleration against time. Acceleration is measured as "g". Time is plotted on the x axis, rate of change of acceleration is plotted on the y axis. Is "dg" a valid label for the "y" axis?

Thanks
 
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  • #2
I'm not clear as to what you are actually plotting. Are you plotting acceleration versus time in order to find the rate of change of the acceleration?

Or are you plotting the rate of change of acceleration versus time, as you state? If the later, you can call the y-axis [itex]\frac{da}{dt}[/itex] or [itex]\frac{dg}{dt}[/itex].

Or are you plotting change of g versus t?
 
  • #3
Hi Doc

I already have rate of change of acceleration (in the vertical direction) measured as rate of change of "g" which I can plot against time, I can then show a certain rate of change of acceleration during a unit of time (in this case 0.01s)

I've assumed that rate of change of acceleration is the same as rate of change of "g", is this correct?

I'm uncertain if the "y" axis should be "dg" or "dg/dt"

Thanks
 
  • #4
Originally posted by Micky
I already have rate of change of acceleration (in the vertical direction) measured as rate of change of "g" which I can plot against time, I can then show a certain rate of change of acceleration during a unit of time (in this case 0.01s)
Are you measuring your acceleration in terms of g the acceleration due to gravity? Or is it just coincidence that you use the letter "g" to refer to acceleration?

It sounds like you are actually measuring changes in g during fixed intervals (0.01 sec) at various times. Is this right? If so then whether you plot Δg or Δg/dt doesn't matter, since they will be proportional. But you better know which you are plotting, since that will determine your label.
I've assumed that rate of change of acceleration is the same as rate of change of "g", is this correct?
You tell me. If you are calling the acceleration "g" (why not call it "a"?) then the rate of change of g is the same as the rate of change of a.
I'm uncertain if the "y" axis should be "dg" or "dg/dt"
What you call the y-axis depends on what you are plotting: are you plotting Δg or Δg/(0.01) ?
 
  • #5
Hi Doc
Are you measuring your acceleration in terms of g the acceleration due to gravity?
Acceleration measured in terms of gravity.
It sounds like you are actually measuring changes in g during fixed intervals (0.01 sec) at various times. Is this right?
Yes.
But you better know which you are plotting, since that will determine your label.
Absolutely.
If you are calling the acceleration "g" (why not call it "a"?) then the rate of change of g is the same as the rate of change of a.
I can certainly call it "a".
What you call the y-axis depends on what you are plotting: are you plotting ?g or ?g/(0.01) ?
Right, I think I see it know :wink: The Y axis is dg, but the graph is dg/t [?]

Thanks Doc

How do you post the delta triangle?
 
  • #6
Ah... You are measuring acceleration "a" in units of "g". Do not call the y-axis "g" or "Δg", call it "a" or "Δa" or "Δa/Δt", depending on what you are measuring.

I still don't know what you are actually measuring. Here's my guess at what your data might look like:
T= 1 sec; Δa = .12 g (measured over a 0.01 sec interval)
T= 2 sec; Δa = .04 g (measured over a 0.01 sec interval)

Etc... Am I even close? What is it that you are measuring the Δa of? How are you making the measurements?

(Note that if you were to list the rate of change of a, it would be measured in units of g/sec not g.)

To find out to make the Δ, just quote this post and look.
 
  • #7
I'm measuring the acceleration of a body in the vertical direction using an accelerometer and datalogger. The raw data is downloaded to a laptop and saved as a text file. The data is presented in two columns, time (measured in units of 0.01s) and acceleration (measured as g). So this means that at any given point in time I know the acceleration of the body.

I load the text file into Excel and calculate how acceleration changes from one measurement to the next, therefore these units must still be g, not Δg [?] ... confused again!

I can then plot a graph of the results of the calculation against time to show the Δg/t [?] [?]

M
 
  • #8
Originally posted by Micky
...
I load the text file into Excel and calculate how acceleration changes from one measurement to the next, therefore these units must still be g, not Δg [?] ... confused again!
I think I see what you are doing now. Your spreadsheet calculates Δa at each time t (I'll bet that you say Δa(at t = n) = a(at t = n+1) - a(at t = n)... or something like that). Good.

Note that "g" is a constant (equals about 9.8 m/s2) so Δg makes no sense. You are going to graph Δa as a function of time. Also note that both a and Δa will have units of "g".
I can then plot a graph of the results of the calculation against time to show the Δg/t [?] [?]
Assuming your spreadsheet finds Δa, your graph would show Δa plotted against time. You will be able to see how the acceleration varies over time.
 
  • #9
Thanks for that Doc :smile:
 

1. What is the definition of "rate of change of acceleration"?

The rate of change of acceleration, also known as the second derivative of position, measures how quickly the acceleration of an object is changing with respect to time. It is a measure of the rate at which an object's velocity is changing.

2. How is the rate of change of acceleration calculated?

The rate of change of acceleration is calculated by taking the derivative of the acceleration function with respect to time. This can be done using the formula: a''(t) = d^2a(t)/dt^2, where a''(t) represents the rate of change of acceleration at time t.

3. What is the significance of the rate of change of acceleration?

The rate of change of acceleration is an important concept in physics and engineering, as it helps us understand the rate at which an object's velocity is changing over time. It is also used to determine the forces acting on an object and can be used to predict an object's future motion.

4. How does the rate of change of acceleration relate to velocity and position?

The rate of change of acceleration is related to velocity and position through the fundamental equations of motion. The first derivative of position is velocity, and the second derivative of position is acceleration. Therefore, the rate of change of acceleration is the third derivative of position.

5. Can the rate of change of acceleration be negative?

Yes, the rate of change of acceleration can be negative. This indicates that an object's acceleration is decreasing over time, or that the object is experiencing negative acceleration (deceleration). This can occur when an object is slowing down or changing direction.

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