What Does the Third Derivative Mean?

  • Context: Undergrad 
  • Thread starter Thread starter x2thay
  • Start date Start date
  • Tags Tags
    Derivative
Click For Summary

Discussion Overview

The discussion centers on the meaning and implications of the third derivative of a function, exploring its significance in various contexts such as physics, mathematics, and engineering. Participants examine its role in determining maxima, minima, and convexity, as well as its applications in differential equations and motion analysis.

Discussion Character

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

Main Points Raised

  • Some participants suggest that the third derivative represents the rate of change of the slope of a function.
  • Others propose that the third derivative can indicate the presence of maxima or minima, particularly when the first and second derivatives are zero and the third derivative is non-zero, with the sign of the third derivative determining the nature of the extremum.
  • A participant provides an example from physics, stating that if a car's acceleration is proportional to the position of the foot on the pedal, then the third derivative (jerk) relates to the velocity of the foot, while the fourth derivative relates to the acceleration of the foot.
  • Another participant emphasizes that the third derivative is simply the third derivative of a function, noting its relevance in certain differential equations where higher-order derivatives may be necessary.
  • A request for more details about the applications of the third derivative and higher derivatives, including specific equations of motion, is made by another participant.

Areas of Agreement / Disagreement

Participants express various interpretations and applications of the third derivative, indicating that multiple competing views remain. The discussion does not reach a consensus on its meaning or applications.

Contextual Notes

Some claims depend on specific definitions and contexts, such as the application of the third derivative in differential equations and its physical interpretations. The discussion includes unresolved questions about the trajectory equations and the roles of higher derivatives.

Physics news on Phys.org
It's the rate of change of the slope of the first graph.
 
Or for example when we want to find a functions maxima or minima, or to determine the convexity of a function. FOr example if f'=f''=0 then if f''' is different from zero the function has a minima of maxima depending on the sign of the f'''.
 
Here's a neat example. Suppose when driving a car, the car's acceleration is proportional to the position of your foot on the pedal. Now if your foot is moving with some velocity, then the third derivative of the car's motion is proportional to the velocity of your foot. And if your foot is moving with some acceleration the then the 4th derivative of the car's motion is proportional to the acceleration of your foot.

The third derivative (the jerk) has some other important implications in physics and engineering.
http://en.wikipedia.org/wiki/Jerk
 
It's the third derivative of a function.
That's its "meaning".

In some approximative schemes of differential equations, it can be advantageous to express one of the unkown functions in terms of the derivatives of another unkown, thereby reducing the number of unkown functions to be found by increasing the order of the resulting diff.eq(s).
Thereby, third-and higher order derivatives may enter in the diff.eq, even if it starts out like at most a second-order problem like Newton's F=ma


The Boussinesq equation types in fluid mechanics are examples of that.
 
Could anyone tell me more detail about third derivative of distance and of others? What does it use for? What about fourth derivative, 5th...?
And my 2nd question is: a mouvement of a object notice by this system equation: x(t)=vxt+x0, y(t)=vy.t+y0, z(t)=vz.t+z0. What is the equation of trajectory, f(x,y,z)=?
Thanks in advance for any reply!

Chhun...
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 15 ·
Replies
15
Views
2K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 2 ·
Replies
2
Views
1K
Replies
2
Views
2K
  • · Replies 21 ·
Replies
21
Views
6K