Power

功率

work

energy

In the straightforward cases where a constant force moves an object at constant velocity, the power is just P = Fv. In a more general case where the velocity is not in the same direction as the force, then the scalar product of force and velocity must be used.

在力恒定且物体以恒定速度运动的简单情况下，功率 simply 为 P = Fv。在更一般的情况下，当速度不与力同方向时，必须使用力与速度的标量积。

The standard unit for power is the watt (abbreviated W) which is a joule per second.

功率的标准单位是瓦特（符号为W），等于焦耳每秒。

功率可以定义为做功的速率或能量使用的速率。这两个定义是等价的，因为使用一单位的能量必须做一单位的功。通常计算平均功率会更方便。

Power Calculation

功率计算

The rate of doing work is equal to the rate of using energy since the a force transfers one unit of energy when it does one unit of work. A horsepower is equal to 550 ft lb/s, and a kilowatt is 1000 watts. 1 hp = 745.8 watts.

做功的速率等于能量的使用速率，因为力在做功时会转移一个单位的能量。1马力等于550英尺磅每秒，1千瓦等于1000瓦。1马力等于745.8瓦。

This calculation is only for cases where the force is in the direction of the velocity, and there are many cases where that is not so. Then for instantaneous power, you just multiply the product of force and velocity by the cosine of the angle between them to get the power. In the more general cases where everything varies, one often calculates the work first and then divides by the time to get the average power.

这个计算仅适用于力与速度方向一致的情况，而有很多情况并非如此。对于瞬时功率，你只需将力与速度的乘积乘以它们之间夹角的余弦值，即可得到功率。在更一般的情况下，当一切都在变化时，通常先计算功，然后除以时间以得到平均功率。

功率 = 牛·米/秒 = 功率 = 瓦特=千瓦功率 = 磅·英尺/秒 = 功率 = 英尺磅/秒=马力

中文译文中的待填/计算数值依次对应：1：f 2：d 3：t 4：p 5：kw 6：fc 7：dc 8：tc 9：pc 10：ph。实际数值以上方原输入框为准。