上一片里，小火箭把箱子搬上了楼，做了一份功 W。可慢慢搬和冲上去，感觉完全不一样——差的就是「快慢」。Last leaf, the rocket carried a box upstairs and did an amount of work, W. But doing it slowly and doing it in a dash feel totally different — the difference is speed.
第 1 步：同样的楼，比谁快Step 1: Same stairs, who is faster?
先看一场比赛——做功的快慢，就叫功率。Start with a race — the speed of doing work is called power.
小火箭和乌龟把同样的箱子搬上同一层楼——做的功 W 一模一样。小火箭 5 秒搞定，乌龟磨了 20 秒。功一样时比时间：时间越短，功率越大。小火箭的功率是乌龟的 4 倍。Rocket and Turtle carry identical boxes up the same floor — exactly the same work W. Rocket finishes in 5 s; Turtle takes 20 s. Same work, so compare time: shorter time, more power. Rocket's power is 4× Turtle's.
那功率到底怎么算、拿什么来量？So how is power calculated — and measured in what?
第 2 步：瓦特，每秒干多少活Step 2: Watts — work per second
算法很简单：功 ÷ 时间，P = W / t。1 瓦特 = 每秒做功 1 焦耳。灯泡就是现成的「功率表」：9 W 的灯每秒耗 9 J，60 W 的每秒耗 60 J，100 W 的每秒耗 100 J——瓦数越大，每秒吞掉的电能越多，灯越亮。1000 W = 1 kW。The recipe is simple: work ÷ time, P = W / t. One watt = one joule of work per second. Bulbs are ready-made power meters: a 9 W bulb uses 9 J every second, 60 W uses 60 J, 100 W uses 100 J — more watts, more energy swallowed per second, brighter light. 1000 W = 1 kW.
那汽车铭牌上的「马力」又是什么？Then what is the “horsepower” on a car's nameplate?
第 3 步：马力也是一种功率Step 3: Horsepower is power too
马力也是功率单位，专用来夸发动机：1 马力 ≈ 735 瓦。一辆 150 马力的车 ≈ 110 kW，意思是它的发动机每秒能做约 11 万焦耳的功。灯泡、发动机、人的腿脚——都能用功率来比「干活的快慢」。Horsepower is another power unit, used to brag about engines: 1 hp ≈ 735 W. A 150 hp car ≈ 110 kW — its engine does about 110,000 joules of work every second. Bulbs, engines, your own legs — all can be compared by how fast they do work.
🎮 你来当裁判（30 秒）🎮 Your turn: referee (30 seconds)
道理讲完了。拖动时间滑块，看两条功率条怎么变；再点「开赛」，看谁先到顶。Theory done. Drag the time sliders to watch the power bars change, then hit “Race!” to see who reaches the top first.
一句话记住它：功率 = 做功的快慢，P = W / t；功一样时，谁快谁功率大。Remember it in one line: power is how fast work gets done, P = W / t — for the same work, faster means more power.
P = W / t：功一样时，时间越短功率越大（同爬一楼，跑上去功率大）P = W / t: same work, less time, more power (run the stairs, out-power the walk)1 W = 1 J/s，1000 W = 1 kW；瓦数越大，电器每秒耗能越多1 W = 1 J/s, 1000 W = 1 kW; higher wattage, more energy per second马力也是功率：1 马力 ≈ 735 W，汽车铭牌用它标发动机Horsepower is power too: 1 hp ≈ 735 W, used on car nameplates
内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.
Back to tree
