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Old 08-09-2012, 05:41 PM   #24 (permalink)
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375 seems okay

Originally Posted by kennybobby View Post
The 375 in the denominator should be 349. (348.66)

That term comes from 0.5 times the conversion factor for mph^3 to (ft/sec)^3 divided by the definition factor for horsepower = 550 lbs-ft/sec.

conversion factor:
mph * 5280 ft/mile / 3600 seconds/hr = ft/sec.

The 375 value assumes a mile is only 5153 ft.
I re-visited my books.And it looks like the 375 value is valid.
Working with the 550 lb'ft/sec value for horsepower calculation requires mph to be multiplied by 5,280 to get feet,then division by 3,600 sec/hr to get it into feet/sec..
If you already have a drag force at a given mph value,to get power,you can use this shortcut,multiplying the force by mph,then dividing by 375.
550/375 yields a constant percentage = to( feet/sec)/(mph) at any given velocity.It's always 1.466X.
Hope that helps!
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