Why Is Horsepower Used for Cars?

Horsepower measures engine capacities of automobiles.

Horsepower is a measure of work done over time, used to compare power and performance of a range of machines. Originated in the late 1700s by the inventor of the steam engine, James Watt, 'horsepower' has become a standard measure of engine capacity. One horsepower is equivalent to 33,000 lb. ft./minute--lifting 33,000 pounds one foot over one minute.

Watt's Engines

James Watt created horsepower to rate his steam engine's capabilities. Watt calculated horsepower based on how much energy a typical horse expends on strenuous activities. Watt observed that a horse grinding corn went around a circle 24 feet diameter 144 times in 60 minutes; from this he deduced the horse's speed to be roughly 181 feet per minute. Taking the speed, and estimating the horse's pulling force to be 180 pounds, Watt calculated one horsepower to be 33,000 lb. ft./minute.

Application

Horsepower may be used to measure the amount of force needed to move a body across a defined distance. As such, the concept is relevant for automobiles. Today, it is widely applied across a range of machines; horsepower is used not just for cars, but for other devices used at homes and industries, such as lawnmowers and vacuum cleaners.

Significance

Horsepower is an important consideration when comparing the engine performance of automobiles. In general, for cars of the same weight, the one with higher horsepower will have more power and will be able to go from 0 mph to 60 mph quicker. High performance vehicles have a higher horsepower to weight ratio, meaning that the vehicle is able to derive more power for each unit of weight.

References

• Cars Direct: Horsepower and How it Works
• Web-Cars: What it Horsepower?