四滑轮

图例：

FZ = 施加在绳自由端的力

FL = 物体重力

s = 绳自由端的位移

h = 物体的位移

这个例子用来说明如何利用合适的滑轮来省力。使用滑轮可以省力但是要花费更多的距离。在每幅图中，所做的功都是相同的。

Description

FZ × s = FL × h　

10 cm × 100 N = 10 J

20 cm × 50 N = 10 J

30 cm × 33 1/3 N = 10 J

40 cm × 25 N = 10 J

FZ = Rope tension or effort force

FL = Load or resistance force

s = Rope displacement (distance pulled) or effort distance

h = Height (distance load is raised) or resistance distance

An illustration showing how pulleys are used to obtain a mechanical advantage. Using additional pulleys decreases the force required but increases the distance required to raise a load the same amount. In each instance here the mechanical work done is the same, work being the product of force and distance.

FZ × s = FL × h　

10 cm × 100 N = 10 J

20 cm × 50 N = 10 J

30 cm × 33 1/3 N = 10 J

40 cm × 25 N = 10 J

通过这个亦可证明功的原理。