A fully loaded semi-truck has a weight of 80,000 pounds Let’s take a theoretical

Question

A fully loaded semi-truck has a weight of 80,000 pounds Let’s take a theoretical truck
and replace its engine with a 5.0HP engine and a suitable gearboxto allow the engine to
produce its rated power continuously. The truck will now bedriven up the I5 freeway
from Santa Clarita to Gorman, an elevation change of 3281feet. Your job is to figure out
how long this trip will take (hint: it’s awhile!) First, convert the English measurements to metricmeasures:   Determine the time (in hours) that the tripwill take. Would you be justified in neglecting wind resistance inthis problem? Why?

Explanation / Answer

1HP = 550ft-lb per sec In other words, a 1HP motor will lift 550lbs at a rate of afoot per second For an 80,000lb truck this would mean 1 foot would take145.455sec with a 1HP motor divide by 5 since you have a 5HP motor and you get 29.0909secper foot Multiply by 3281 feet to get 95,447.3 seconds Wind resistance isn't feasable as it changes over time and isnot constant 80,000lb/(5HP)(550ft-lb per sec) = 29.0909sec/ft 29.0909sec-ft(3281 feet) = 95,447.3 sec

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