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

`t=30.5s`

Step-by-step 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)=(U)/(t)\\ P_(man)=(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*((562.5lb.ft/s)/(746W) )=73.73lb.ft/s\\t=(U)/(P_(bulb))=(2250)/(73.73) \\ t=30.5s`