Horsepower is an imperial unit of power of an engine. It is defined as the work done per unit time. The term Horsepower was invented by James Watt. It is a unit power that compares the power of a machine to the horse muscle power. Earlier it was used to measure steam engine power output compared to the power of draft horses. Later it was expanded to different types of piston engines, electric motors, turbines and other machinery.
One Horsepower equals to 33,000 lb. ft/min.
Horsepower formula is given as
Horsepower (HP) = (Torque × Speed)/5252
There is another Horsepower formula related to the weight given as
This formula is applied to calculate the speed or velocity at the end of the run. Weight includes the mass of the whole body.
Example 1
Determine the horsepower of a car which moves with a speed of 600 revolutions per minute and has a torque of 100 pound-foot.
Solution:
Given parameters are
Torque = 100 pound-foot
Speed = 600 revolutions per minute>
Horsepower formula is given by
Horsepower = (Torque × Speed) / 5252
HP = (100 × 600) / 5252
HP = 60000/5252
HP = 1.142 hp
Example 2
Calculate the speed of the vehicle if its horsepower is 0.865 hp and torque is 250 pound-foot.
Solution:
Given parameters are
Torque = 250 pound-foot
Horsepower (HP) = 0.865 hp
The speed is given as
Speed = (Horsepower × 5252)/ Torque
Speed = (0.865 × 5252)/ 250
Speed = 4542.98/250
Speed = 18.17 revolutions per min
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