quick power/hp question

anonymous820

1. The problem statement, all variables and given/known data

how do u get from power to horsepower?
mass=60 kg
weight=588.6 N
height=7 m
time=6.45 s
power= 638.79 W

2. Relevant equations

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3. The attempt at a solution

multiply by 746 W to get: 476537.34 hp
or divide by 746 W to get: .856286 hp

i think its divide rather than multiply b/c then the watts cancel and ure left with hp, but im not sure. thats my only question. multiply or divide?

mgb_phys

1 horsepower = 745.7 watts
or 1 W = 1/745.7 Hp, so you replace the 'W' with (1/745.7)Hp.

Or just think would 638W be more or less than 1 hp and roughly how many would it be?
It's always worth estimating the answer before putting the numbers in a calculator.

anonymous820

less. so IT IS divide. thanks. i knew 400,000 hp was unreasonable for a person. this was a lab btw.

berkeman

You have the correct instinct that you should be able to carry your units along in your calculation to help you keep the numbers in the right places. Here's a thread that should help your insight -- check out my post #10 and the subsequent comments:

http://www.physicsforums.com/showthread.php?t=130989

Very important trick to use and master in your math and physics and engineering studies!