Work says how much; power says how fast. $P = \dfrac{W}{t}$ (read aloud: P equals W over t) — the power $P$ in watts, the work $W$ in joules, the time $t$ it took in seconds — and its unit, the watt, is one joule per second. Same bill, different clock: a kettle and a campfire can hand the water the same joules, but the kettle does it before the conversation dries up.

Power's second face: push with force $F$ at steady speed $v$ and $P = Fv$ (P equals F v) — newtons times metres-per-second cancels to joules-per-second, the units signing off. Choose the face by the GIVENS: work and time point to $W/t$; force and speed point to $Fv$. And mind the chapter's running gag — W the symbol is work in joules, W the unit is watts. The sentence tells you which one showed up.