Jerk (physics)

The jerk (symbol: , of Engl jerk or jolt. ) Is a term from the kinematics, which is used primarily in the dynamics and the transmission teaching. It is the derivative of the acceleration with respect to time, that is, the second time derivative of the speed, and the third time derivative of the position vector:

Wherein the time of acceleration, speed, and the location is. The SI unit of jerk accordingly.

A jolt upset with elastically suspended systems to vibrations.

Application

This physical meaning of " jerk " is largely the same as the colloquial meaning of the word. However, colloquially, the jerk is judged in part by the total velocity change of a system with a short-term acceleration.

In vehicles the reason for jerks is often a load change (eg during partial load bucking). A distinction is made between longitudinal and lateral jerk. The longitudinal jerk means a temporal change of the tangential acceleration. The cross jerk on the other hand represents a temporal change of radial acceleration.

For longitudinal jerk in vehicles:

The faster braking is initiated or terminated, the higher the jerk. An abrupt initiated braking ( emergency brake ) is associated with a high jerk. If the occupant does not set fast enough and it is supported, it is thrown when moving forward to the front ( trapped by the belt in the car ) down when driving backwards into the seat. Since the operation of the brake or claims a minimum amount of time even in an emergency, the residue is a finite value.

If the brake to a stop at its maximum power effective, occurs at the end of the braking distance on a theoretically infinitely high jerk, because the delay ( = neg acceleration) suddenly, that ends at time zero. This is the occupant by his own muscle power ( support force ) or, if he has behaved completely passive, hurled by the force exerted by the belt force on the chair and then thrown back by the spring force of the chair. However, time is consumed for these movements, which means that the jerk is finite, therefore mitigated. In addition, elastic elements relax on the vehicle, from the tire on the wheel suspension, etc., which also takes at least minimum time.

In normal operation, the veteran driver releases the brake slowly before reaching the standstill and thus prolongs the decrease in the delay of time so that the jerk is reduced to a minimum.