Is a 200 hp car really equivalent to a traction of 200 hp?
The term horsepower, measuring how much power an engine can produce, is known even to ordinary car enthusiasts. The higher the number, the more likely the car is to win the race.
Show key points
- Horsepower, originally devised by James Watt, was created to help market steam engines by comparing their power to that of workhorses.
- Watt defined one horsepower as the ability to move 33,000 pounds one foot in a minute, which equates to roughly 746 watts.
- Despite its name, a real horse can only sustain about 1 horsepower over time, though it can peak at around 1
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- 9 to 24 horsepower briefly.
- There are various definitions of horsepower depending on the context, such as mechanical (imperial), metric (PS), electric motor horsepower, and boiler horsepower.
- The term "metric horsepower" (Pferdestärke) is commonly used in Europe and represents about 73
- 5 watts of power.
- Cars may start with high horsepower ratings, but engine wear, clogged filters, and other issues can decrease actual performance over time.
- Although a 200-horsepower car is not the same as being pulled by 200 horses, this unit still serves as a useful measure of engine output.
But how much horsepower does a horse have? Is a 200 hp car really equivalent to being pulled by 200 hp? Quite simply, no, and this is a common misconception. It turns out that there is a little more.
An actual horse can produce a maximum power of 15 horsepower. As for man, he can reach a horsepower equivalent to one. Although it seems strange that horsepower is not equal to horsepower, there is an explanation. Below, we'll learn a little bit about where the term "horsepower" originated, and what it actually means.
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What is horsepower?
Engineer James Watt developed the Horsepower Expression, a quantity intended to measure the power of a steam engine, as its improved steam engine design was more efficient than previous designs and required much less fuel. Therefore, he developed horsepower as a way to prove to customers who have not yet switched from horses to steam engines that this is a good investment.
He calculated that during an average workday, a horse could turn a 24-foot mill wheel about 2.5 times per minute. Power is defined as the work done per unit of time, where the work is a measure of the energy transported, calculated by multiplying the applied force by the distance traveled.
Watt, the same name for the power unit in the metric system, estimated how much force the horse applied to spin the mill wheel. Using this, he then calculated the amount of energy applied, and therefore the power.
Watt knew that the number he got was just an estimate, so he chose to round his account to get his final score.
According to Watt's definition, a single horsepower is 33,000 feet per minute. This is approximately equal to 746 watts (W, or joules per second).
Modern car manufacturers use the definition of watts and a similar amount known as metric horsepower. Metric horsepower is defined as the ability needed to lift a mass of 75 kilograms against gravity for a distance of one meter in one second. This amounts to about 735 watts.
How much horsepower does a horse have?
Watt's estimates were fairly accurate: a single horse is roughly the average rate of work a healthy traction horse can do over the course of a full day, which was confirmed by data from the 1925 Iowa State Fair and English veterinary surgeon William Yoat.
In 1993, biologist R.D. Stevenson and R. G. Vassug wrote a letter to Nature, where they maximized the maximum capacity a horse could mass. Previous studies have shown that the maximum sustainable mechanical capacity per kilogram of muscle is between 100 and 200 watts. Using the minimum, they calculated a theoretical peak performance of 18,000 watts, or about 24 horsepower.
Looking at data from the 1925 Iowa State Fair, they found much less value in the real world. According to their calculations, in a short period of time, a horse can exert up to 14.9 horsepower.
How can horsepower have different definitions?
Unlike measuring time, for example, the exact definition of horsepower can vary depending on regional differences and the specific machine whose power is being measured.
Mechanical horsepower, also known as imperial horsepower, is a measurement devised by James Watt and is roughly equivalent to 745.7 watts of power. The Pferdestarke, also known as PS or metric horsepower, is a similar measurement developed in Germany and is equivalent to 735.5 watts.
The horsepower of electric motors is equivalent to 746 watts, while the horsepower of a boiler, which is used to measure the production of steam boilers, is more different, with the horsepower of a single boiler approximately equivalent to 9810 watts.
Why do cars lose horsepower over time?
When it comes to your car, the most commonly used measure of engine power and power is Horsepower, or bhp.
While your engine may, for example, produce 200 horsepower, the different mechanical parts of your drivetrain mean that this power won't reach your wheels in its entirety.
Things tend to get dirty and wear over time as air filters and exhaust can clog, blocking airflow to and from the engine and so on. So, keep your car regularly maintained, and a modern engine should lose only a fraction of horsepower over hundreds of thousands of miles.
