|  | 
			
			
			
					
					
			
				
					
						
	x -> position
		
			
			
				
					  Originally Posted by Poopadoop   What the highest-order derivative that has a use in the real world?
 For example, in movement we sometimes measure jerk (second derivative of velocity, or third of position) as a measure of "smoothness" of a movement, but nothing beyond that. Is there anything in any domain that goes higher than that and what's it used for?
 (d/dt) x -> velocity
 (d/dt)^2 x -> acceleration
 (d/dt)^3 x -> jerk
 (d/dt)^4 x -> snap
 (d/dt)^5 x -> crackle
 (d/dt)^6 x -> pop
 
 and no, I'm not even joking about the last 3.
 
 Off the top of my head, elasticity theory frequently uses the 4th derivative, but it's a spacial derivative, not a time derivative.  I.e. (d/dx) instead of (d/dt).  Elasticity theory covers how materials change shape when forces (loads) are applied.  This describes how an object in bending will bend such that it minimizes the curvature for a given loading.
 
 It also applies in civil engineering when determining how a road should bend.  Minimizing the 4th derivative (w.r.t. space) makes for smooth turns.
 
 
 I do not know of any branch of physics or engineering that regularly uses a higher order derivative.
 |