Horsepower

Horsepower is a unit of measurement of power, or the rate at which work is done. There are many different standards and types of horsepower. Two common definitions being used today are the mechanical (or imperial) horsepower, which is about 745.7 watts, and the metric horsepower, which is approximately 735.5 watts.

The term was adopted in the late 18th century by Scottish engineer James Watt to compare the output of steam engines with the power of draft horses. It was later expanded to include the output power of other types of piston engines, as well as turbines, electric motors and other machinery.

History

The concept of horsepower was developed by the Scottish engineer James Watt. In the early 18th century, Watt was working with ponies lifting coal at a coal mine, and he wanted a way to talk about the power available from one of these animals. He found that, on average, a mine pony could do 22,000 foot-pounds of work per minute. He then increased that number by 50 percent and pegged the measurement of horsepower at 33,000 foot-pounds of work in one minute. It is that arbitrary unit of measure that has made its way down through the centuries and now appears on your car, your lawn mower, your chain saw and a variety of other machines.

Calculating Horsepower

Horsepower can be calculated in various ways. The most common method is by using the formula:

Horsepower = Torque x RPM / 5252

Where:

• Torque is in pound-feet
• RPM is the speed the engine is spinning at
• The constant 5252 is the rounded value of (33,000 ft·lbf/min)/(2π rad/rev)

Types of Horsepower

There are several types of horsepower:

• Mechanical (or Imperial) Horsepower - Defined as approximately 745.7 watts.
• Metric Horsepower - Defined as approximately 735.5 watts.
• Boiler Horsepower - Used in the industrial boilers, commonly calculated as 10 sq. ft of boiler heating surface.
• Electrical Horsepower - Used in the US and is equal to exactly 746 watts.
• Hydraulic Horsepower - Reflects the power that a hydraulic pump can produce.

See Also

• Power (physics)
• Engine
• Watt
• Torque

References

Horsepower Resources
Need Help Finding a Doctor? Need help finding a doctor or specialist anywhere in the world? Explore our world directory. WikiMD's DocFinder can assist you in locating millions of physicians.	Medical Knowledge Access the latest research - Most recent articles Ongoing trials.

Translate to: East Asian 中文, 日本, 한국어, South Asian हिन्दी, Urdu, বাংলা, తెలుగు, தமிழ், ಕನ್ನಡ,
Southeast Asian Indonesian, Vietnamese, Thai, မြန်မာဘာသာ, European español, Deutsch, français, русский, português do Brasil, Italian, polski