Jerk (physics)
In physics, jerk, also known as jolt (especially in British English), surge and lurch, is the rate of change of acceleration; that is, the derivative of acceleration with respect to time, the second derivative of velocity, or the third derivative of position. Jerk is defined by any of the following equivalent expressions:
where
- is acceleration,
- is velocity,
- is position,
- is time.
Jerk is a vector, and there is no generally used term to describe its scalar magnitude (e.g., "speed" as the scalar magnitude for velocity).
The SI units of jerk are metres per second cubed (metres per second per second per second, m/s3 or m·s−3). There is no universal agreement on the symbol for jerk, but j is commonly used. Newton's notation for the derivative of acceleration can also be used, especially when "surge" or "lurch" is used instead of "jerk" or "jolt".
If acceleration can be felt by a body as the force (hence pressure) exerted by the object bringing about the acceleration on the body, jerk can be felt as the change in this pressure. For example a passenger in an accelerating vehicle with zero jerk will feel a constant force from the seat on his or her body; whereas positive jerk will be felt as increasing force on the body, and negative jerk as decreasing force on the body.
Note also the existence of yank—the derivative of force with respect to time.
Read more about Jerk (physics): Applications, Non-calculus Explanation
Famous quotes containing the word jerk:
“One farmer says to me, “You cannot live on vegetable food solely, for it furnishes nothing to make bones with;” and so he religiously devotes a part of his day to supplying his system with the raw material of bones; walking all the while he talks behind his oxen, which, with vegetable-made bones, jerk him and his lumbering plow along in spite of every obstacle.”
—Henry David Thoreau (1817–1862)