Question

The man having the weight of 150 lb is able to run up a 15-ft-high flight of stairs in 4 s. Determine the power generated. How long would a 100-W light bulb have to burn to expend the same amount of energy? Conclusion: Please turn off the lights when they are not in use!

Answer 1

Answer:

$t=30.5s$

Explanation:

Given data

The weight of man W=150 lb

The man can run up stairs of height h=15 ft in time t=4s

The work done by man

$U=Wh\\U=(150)(15)\\U=2250 lb.ft$

The power generated by the man

$P_{man}=\frac{U}{t}\\ P_{man}=\frac{2250}{4}\\ P_{man}=562.5lb.ft/s\\or\\P_{man}=562.5lb.ft/s*(1/550)=1.02hp$

Power of bulb

$P_{bulb}=100*(\frac{562.5lb.ft/s}{746W} )=73.73lb.ft/s\\t=\frac{U}{P_{bulb}}=\frac{2250}{73.73} \\ t=30.5s$