# Step 5 plug in substitute what you know and you will

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Step 5: Plug in (substitute) what you know and you will find out what you don't know:
(b) What is the elevator's power output?
Step 2: Write down what you don't know in symbolic form:a. Work = ?b. Power: P = ?Step 3: Find an equation that contains what you know and what you don't know:a. Work = Fdb. Power: P = work/t; but work = answer to part a.Step 4: Solve the equation for what you don't know:The equations are in the form we need. Step 5: Plug in (substitute) what you know and you will find out what you don't know:a. Work = Fd, where F = ma = mg; but mg = weight (W) which is given as 9,800N.Work = Fd = Wd = 9800 N x 28 m = 274,400 N-m = 274,400 Jb. Power: P = Fd/t = 274,400 J/ 19 s = 14,442.1 W
Q9It takes 110 minutes for a middle-aged physics professor to ride his bicycle up the road to Alpe d'Huez in France. The vertical height of the climb is 1,120 m, and the combined mass of the rider and bicycle is 95 kg. What is the bicyclist's average power output?
Step 2: Write down what you don't know in symbolic form:What is the bicyclist's average power output?Step 3: Find an equation that contains what you know and what you don't know:
Q10When you throw a ball, the work you do to accelerate it equals the kinetic energy the ball gains. If you do twiceasmuch work when throwing the ball, does it go twice as fast? Explain.
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