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Horsepower of a Truck

by pippintook
Tags: engine, horsepower, physics, power, work
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pippintook
#1
Jan28-09, 05:02 PM
P: 17
A 40,000 kg truck traveling on I-70 leaves Denver (elevation 5280', mile marker 244) and goes over Rabbit Ears pass (elevation 11,840', mile marker 238) while maintaining 50 mph. What is the horse power rating on his engine?


The formulas I used are as follows:

power = work/time

work = (mass)(gravity)(height)

746 watts = 1 horsepower


To solve for time I did 50 miles/60 minutes = 6 miles/x minutes and got 7.2 minutes (or 432 seconds).

After putting in all of these numbers I got 57,442 horsepower. This doesn't seem to make sense though, as that is a LOT of horsepower. I think the problem may be the height, since I put in the change of height (6560 feet). Help please? Suggestions?
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mgb_phys
#2
Jan28-09, 06:08 PM
Sci Advisor
HW Helper
P: 8,953
Put everything into metres, seconds and kg, I suspect you have got the units mixed up.

Hint - you only care about the vertical speed.


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