Cars did not have time to appear, as PR penetrated into the automotive sphere. And no wonder, in the 18th century, when steam engines only appeared, the acute question arose of their advancement to the masses. It turned out that selling your invention, having formed a positive attitude and knowledge of future buyers, is as difficult as inventing the steam engine itself.
During the sale of his invention - a steam engine, an Englishman, James Watt, could not explain to customers what the power of the engine was and what its advantages were. Then it occurred to him to compare a steam engine with a horse, the power of which customers imagined very well.
James Watt began to watch horses in coal mines pulling baskets of coal onto the surface of the coal mines and calculated that on average in one minute a horse would lift a load of 330 pounds (149.7 kg) to a height of 30 feet (9.144 m). The inventor took this ratio as a new unit of measure and coined it the name “horsepower”.
However, feet and pounds were not used in all countries, and he recalculated "horsepower", taking as a basis the speed of one second. In this case, horsepower is equal to the power that needs to be developed in order to lift a load weighing 75 kilograms to a height of 1 meter in one second. This unit of measure has become used around the world. But in 1960, at the 11th General Conference on Weights and Measures, a new unified International System of Units SI (SI) was adopted. In this system, power is not expressed in horsepower, but in watts.
By the way, according to scientists, for a short time a horse can work with a maximum load of almost 15 horsepower.