# What is Jerk?

1. Oct 7, 2005

### AMF8

What is Jerk? I have a rough idea of what it is, but I would like to know more.

2. Oct 7, 2005

### Danger

Maybe try running a quick search. I know that this was addressed recently somewhere in PF, and I believe the response came from Astronuc.

3. Oct 7, 2005

### arildno

It is the rate of change of acceleration.

4. Oct 7, 2005

### Danger

Given the nature of our GD interactions, I'm surprised that my name didn't enter into your response.

5. Oct 7, 2005

### arildno

I knew you knew it, but you know so much that it takes a while even for you to rummage through all your knowledge. You're only superhuman.

6. Oct 7, 2005

### Danger

I didn't mean that; I meant because I'm a jerk. (And I didn't know the answer. I just knew that I saw it mentioned somewhere. )

7. Oct 7, 2005

### cronxeh

Jerk is the 3rd derivative of the position vector

1st derivatieve is velocity, 2nd is acceleration, 3rd is jerk, etc

8. Oct 9, 2005

### AMF8

I know all of that.....what is its purpose?

9. Oct 9, 2005

### jcsd

There's very many posts on 'jerk' in the arhive, it's a recurring subject (you can sya I posted about jerk in this very forum just yesterday!).

Many important examples of objects in motion with a non-conatnt accelartion clearly exist in physics, for example simple harmonic motion, but simply becasue the accelartion is not necessarily mean that it is useful to know the jerk of the object.

There usual exmaple of an area (in engineering) where knowing the jerk is useful is rollercoaster design. It is generally agreed that non-constant accelartion in the car as it goes around the track is what gives the ride it's sense of danger, so it is useful to measure the jerk.

10. Oct 9, 2005

### Mk

11. Oct 10, 2005

### arildno

To be mean?

12. Oct 11, 2005

### Mk

If you're... in a bumper car, and you're going at whatever constant acceleration, towards your stationary sleeping friend, and you smash into him, you're going to be changing your rate of acceleration.

13. Oct 11, 2005

AMF8,