Hello I'm a senior (12th grade) Physics student and I have a question in my work that goes like this...

"A 150-lb. man runs upstairs to a floor 10 feet above him in 5 seconds. What is his power output in horsepower?"

I've searched the website for other questions like mine but they didn't really help me. Any help would be much appreciated, Thanks!

Power is the amount of work done per unit time, and is also equal to the force applied times the velocity in the direction opposing that force. So you can do this two different ways:

1. Calculate the amount of work done to raise 150 pounds by 10 feet against gravity (Work = mgh). Then divide by the time it took to calculate power.

2. Power can also be found by multiplying the force applied to an object times its velocity against that force. So here you have the man's weight as the force, which you multiply by his vertical velocity of 10 ft/5 sec.

Either way you get the same answer.

Thabks a lot!