what is horsepower? how do you determine it? why is it called horsepower? can someone please just explain horsepower in general to me i’m so confused why doesn’t it have anything to do with horses? ):
In: Engineering
I absolutely has to do with horses. Horses were the main source of moving stuff pre automobile; so everything a car did was compared to a horse and carriage or horse and wagon (also steam trains which I guess came before cars)
A horsepower is defined by the force it takes to move 550 lbs 1 foot in one second
Power is a measure of how much energy can be used or transferred in a given amount of time.
Fundamentally, it boils down to force * distance / time. In an engine or motor that force is usually rotational, so it’s torque * rate of rotation. Different units have different constant scaling factors.
horsepower came from the marketing department trying to sell steam engines to people that used horses to drive their machinery. A more sane unit of power is watts. 1 watt = 1 newton of force applied for 1 meter of distance in 1 second of time. 1 watt is also equal to 1 amp at 1 volt.
1 horsepower is about 746 watts.
The guy who invented the steam engine, Watt, wanted to sell his invention, and he saw that the engine was supposed to replace horses. He came up with the word “horsepower” as a marketing strategy. He measured how much power a horse can produce for this purpose.
Today, both energy units we commonly use came from Watt, where 1 hp = 750W (approximately)
A horse can actually generate up to 15 hp, and an average human can generate up to 1.2 hp during maximum output.
https://spark.iop.org/why-one-horsepower-more-power-one-horse#:~:text=The%20horsepower%20unit%20derives%20from,power%20delivered%20by%20a%20horse.
In physics power can be defined as force applied to an object over a distance during a specific time or P = F * (D/T).
For example, if you were pushing a box down a hallway and it took you 10 minutes, we could define how much power you used based on how much force you had to apply to move the box and how long the hallway was (since we already know the time).
Prior to the invention of motors, animals were the primary source of a lot of power (other than humans). Mules might turn a grinding wheel, oxen might pull a plow, horses would pull a cart, etc. When people started selling motors it made sense to compare it to a commonly used animal and for a lot of the tasks the engines were being used the main animal was the horse. Of course every horse is different, so a sort of average or common value was created to represent a standard horse.
James Watt (whom the unit Watt is named after) performed experiments to measure how much power a horse could generate to try to come up with this unit. After experimenting they set the value to be 33,000 foot-pounds (44,742 J) per minute which is about 746 Watts (the metric unit of power), this is the imperial horsepower value. There is a separate metric horsepower value of 735.5 Watts as well, just to make things confusing.
Watt’s original experiment for measuring horsepower was based on how many times a horse could turn a mill wheel in one hour. The later standardized definition based on that experiment was the power required to lift 550 lbs by 1 foot in one second. The metric horsepower was then defined as the power required to lift 75 kg by 1 meter in 1 second.
To measure horsepower today there are various methods and equipment, but they would all be calibrated to the known imperial and/or metric standard.
It’s for the same reason why LED light bulbs are marketed as 60W equivalent, because that is what the customer understands.
You are a farmer in 1910. On your farm you have 2 horse animals to pull a plow. You want to buy a diesel tractor. How powerful of a tractor do you need? What’s a Watt?
Horsepower is a unit of power that represents the kind of average power from a horse per day. One horse animal produces more than 1 HP for a little while but not 12 hours a day. You could get rid of your horse and replace it with a 1 hp water pump running continuously for example.
It’s a unit of power.
Power is work done over time.
Work is force exerted across a distance.
Force is the acceleration of a mass.
Acceleration is the change in velocity over time.
Velocity is the change in distance over time.
Generally, we use watts for power.
1 horsepower = 745.7 W = 550 ft*lbs/s
To put what we described earlier into math,
Watts = joules/second
= Newtons * meters/s
= kilograms * m/s^2 * m/s
= kg*m^(2)/s^3
A horsepower was defined as the average amount work a horse could do over the course of a day (note: work/time). When engines became a thing, it was useful to compare their output to something people knew, which was a horse.
If it took 2 horses all day to plow a field, a 20 horsepower tractor could plow 10 fields in a day.
A horse at its maximum can output about 15 horsepower, but it’s not sustainable over the course of a day, since the horse needs rest.
The real question is, would duckpower be a better alternative than using horsepower?!
Let’s talk about modern terms.
Cars are measured in torque and horsepower.
To put it in simple terms, torque is the amount of work an engine produces. Horsepower is how fast it can do that work.
Horsepower is an ill-defined and useless unit. It should not be used. There is no exact definition of how much power it is precisely, but it’s somewhere around 750W. Originally, it was a marketing gimmick by Watt to compare his engines to work done by horses.
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