# Homework Help: Quick power/hp question

1. Jan 14, 2008

### 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?

2. Jan 14, 2008

### 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.

Last edited: Jan 14, 2008
3. Jan 14, 2008

### anonymous820

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

Last edited: Jan 14, 2008
4. Jan 14, 2008

### Staff: Mentor

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:

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

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

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