The amount of friction is designed to be some degree less than the return spring, so that when the pedal is released, it returns to the closed position.
设计时要确保总摩擦力小于折回弹簧的弹力，这样当松开踏板时，弹簧才会弹回，油门才会闭合。
2
But the friction (hysteresis) makes it easier to maintain a steady throttle setting, and relieves strain from pushing against the spring continuously.
但摩擦力(滞后作用)可以保证更平稳地完成油门设定，并缓解在持续挤压弹簧过程中产生的张力。
3
This always applies both for conservative forces, like gravitational and spring forces, but it also holds for nonconservative forces such as friction.