Sunday, February 25, 2024

How To Calculate Horsepower Physics

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Tractive Effort Estimation Formula#

calculating horsepower of accelerating car

I do not take credit for this excellent formula. I found it in a paper by Virginia Tech on Rail Resistance Equations. It is located on page 11.

  • T is Tractive Effort, in Newtons.

  • P is Horsepower. Remember, the output horsepower, not the maximum horsepower!

  • V is the velocity in km/hr.

  • n is the locomotive’s efficiency in converting power output to tractive effort. For the F7, I found ~0.72 is best.

You might wonder…how accurate is this?

For the F7, within 0.75%.

The other way that you could find tractive effort, of course, is by using a table of measured values, however these are hard to find for many locomotives. I tested this equation against a known table of values for the EMD F7, and by tuning the efficiency coefficient I was able to get an average percent error of 0.33%. I deemed this acceptable, so this guide will be using this formula for tractive effort unless a better method comes along.

Whats My Best Formula To Use To Calculate Horsepower Or Torque From Acceleration Data

Jeff Reid said:You need to know the weight of the car. You also need to measure the rate of deceleration with the clutch depressed, which will let you calcuate the drag factors. You’ll probably need to do a curve fit for the drag factors .Given that, then you can determine the net force during each frame interval by the rate of acceleration times mass of the car. The force at the driven tires equals the net force + drag force. The power at the rear tires equals this force times speed.To determing horsepower = force x speed / 375

What is the 375 from?

Deutsches Institut Fr Normung 70020

DIN 70020 is a GermanDIN standard for measuring road vehicle horsepower. DIN hp is measured at the engine’s output shaft as a form of metric horsepower rather than mechanical horsepower. Similar to SAE net power rating, and unlike SAE gross power, DIN testing measures the engine as installed in the vehicle, with cooling system, charging system and stock exhaust system all connected. DIN hp is often abbreviated as “PS“, derived from the German word Pferdestärke .

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What Is The Genesis Of Horsepower

To understand the basic concept of horsepower we have to look at its origin in the 18th century. The creation of a steam power system was about delivering the required amount of power. At this moment in time an engineer James Watt , was trying to work for the betterment of the steam engine concept. Watt took notice in the working phenomenon of horses that dragged, pushed, and lifted heavyweight in workshops, mills, and pits. He was considering a method to demonstrate that his industrial steam engine possibly will out workhorses and he laid the foundations of horsepower after that.

What Is Tractive Effort#

How to Calculate Horsepower: 12 Steps (with Pictures ...

On a locomotive, the linear output force is called tractive effort. Because of how Back-EMF affects electric motors, the faster a motor spins, the less current it draws, and consequently, the less force it outputs. The specifics behind this decline in tractive effort get very complex, but the principle is simple:

The higher your speed, the lower your locomotive’s tractive effort.

This decline is not linear it happens in an exponential curve.

With this in mind, there are two places we can get tractive effort:

  • Starting Tractive Effort, found in the locomotive data sheet, is the rated tractive effort starting from a standstill in RUN8. On the F7, this is 56,500lbs.
  • The Tractive Effort estimation formula, which I found in a paper from Virginia Tech University.

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How To Become Powerful

Considering the definition of power and the two ways to find it yields multiple ways to increase something’s power: increase its strength or get the same work done faster . A powerful car is strong and fast, and a weak one is neither. The more easily and quickly work can be done, the more powerful the entity doing the work.


  • How to increase power: Get more done in a shorter time period.

This also implies that a very strong machine, say a highly muscular bodybuilder, could still lack power. A person that can lift a very heavy load, but only very slowly, is less powerful than someone who can lift it fast.

Similarly, a very fast machine or person that doesn’t get much done, someone rapidly flailing in place but getting nowhere, is not actually powerful.

Horsepower = / 63025 = 0286

63,025 is a constant when using RPM for speed and in-lbf for torque units. 5,252 is another common constant if the speed is in RPM and torque is in ft-lbf. If the units are different then simply make the unit conversion.

The derivation of these constants is done using the 33,000 ft-lbf /min = 1 horsepower. Though horsepower units are a derivative of the 33,000 ft-lbf/min, it is not critical to understanding how to calculate motor horsepower for speed and torque.

Another common unit of power that motors are rated in is watts. The conversion from watts to horsepower is 745.7 watts = 1 hp.

To assist designers with sometimes difficult unit conversions Groschopp has developed The MOTORTEC STP calculator, a free, downloadable program that provides a fast, easy way to calculate speed, torque, or power. Conversions of the most commonly used units are selectable, automatically generated and can be printed out.

  • Calculate Speed, Torque and Power
  • Calculate Estimated Electrical Current and Losses for Optimum Motor Selection
  • Easily and Accurately Convert Units of Measurement
  • Customizable, Printed Report Function

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How Is Horsepower Measured By Using Calculator:

The calculator is 100% free and specifically designed with a user-friendly interface through which you can easily perform calculations.

Swipe on!


  • First of all, enter the weight of the vehicle in kgs or in lbs.
  • Then, put the elapsed time in sec/min/hrs that is taken by vehicle to cover the quarter mile.
  • Hit the calculate button.
  • Engine power in mechanical horsepower.
  • Engine power in metric horsepower.
  • Engine power in kilowatts.
  • Engine power in foot-pounds per second.
  • Engine power in electrical horsepower.
  • Engine power in boiler horsepower.

Work And Kinetic Energy

Torque and Power Calculations – For Watts and Horsepower!
  • Relate the work done during a time interval to the power delivered
  • Find the power expended by a force acting on a moving body

The concept of work involves force and displacement the work-energy theorem relates the net work done on a body to the difference in its kinetic energy, calculated between two points on its trajectory. None of these quantities or relations involves time explicitly, yet we know that the time available to accomplish a particular amount of work is frequently just as important to us as the amount itself. In the chapter-opening figure, several sprinters may have achieved the same velocity at the finish, and therefore did the same amount of work, but the winner of the race did it in the least amount of time.

We express the relation between work done and the time interval involved in doing it, by introducing the concept of power. Since work can vary as a function of time, we first define average power as the work done during a time interval, divided by the interval,

Then, we can define the instantaneous power .


Power is defined as the rate of doing work, or the limit of the average power for time intervals approaching zero,

If the power is constant over a time interval, the average power for that interval equals the instantaneous power, and the work done by the agent supplying the power is W=P\Delta t . If the power during an interval varies with time, then the work done is the time integral of the power,

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How To Use The Hp To Amps Calculator

Let’s say we want to find the current flow in an AC single phase motor. The engine’s designed power is 1 hp, and it works with a voltage equal to 200 V. The engine’s efficiency is 90%, while the power factor is 0.92. Let’s work out the result step by step using the appropriate horsepower to amps formula:

  • Estimate the power in watts , 1 hp * 746 = 746 W

  • Evaluate the product in the denominator, 200 V * 0.92 * 90% = 165.6 V. You can always convert decimal to percent to make your life easier

  • Make a fraction of these numbers and find the final horsepower to amps value, 746 / 165.6 = 4.505 A. We round the outcome to four significant figures.

  • In this case, a 1 hp motor to amps gives 4.505 A.

  • You can also use our tool as an amp to hp calculator. Take a look at the next example:

    What is the motor’s nominal power if it runs with the applied three-phase line-to-line voltage of 100 V, the flowing current equals 0.5 A, while the efficiency and power factor are 95% and 0.8, respectively? Let’s see how to solve it:

  • Rearrange the formula of hp to amps for the three-phase line-to-line system P = I * 3 * V * PF* / 746

  • Apply the values , P = 0.5 * 1.73 * 100 * 0.8 * 95% / 746

  • The resulting power equals 0.088 hp

  • We can also rewrite the outcome using scientific notation, P = 8.8*10² hp. And that’s how you convert amps to hp!

  • Note that we are using approximations in these calculations, so we strongly recommend to use our hp to amps calculator to get the precise results!

    Society Of Automotive Engineers/sae International

    Early “SAE horsepower” ” rel=”nofollow”> RAC horsepower for the formula)

    In the early twentieth century, a so-called “SAE horsepower” was sometimes quoted for U.S. automobiles. This long predates the Society of Automotive Engineers horsepower measurement standards and was another name for the industry standard ALAM or NACC horsepower figure and the same as the British RAC horsepower also used for tax purposes. Alliance for Automotive Innovation is the current successor of ALAM and NACC.

    SAE gross power

    Prior to the 1972 model year, American automakers rated and advertised their engines in brake horsepower, bhp, which was a version of brake horsepower called SAE gross horsepower because it was measured according to Society of Automotive Engineers standards that call for a stock test engine without accessories , and sometimes fitted with long tube test headers in lieu of the OEM exhaust manifolds. This contrasts with both SAE net power and DIN 70020 standards, which account for engine accessories . The atmospheric correction standards for barometric pressure, humidity and temperature for SAE gross power testing were relatively idealistic.

    SAE net power

    SAE certified power

    In 2005, the SAE introduced “SAE Certified Power” with SAE J2723. To attain certification the test must follow the SAE standard in question, take place in an ISO 9000/9002 certified facility and be witnessed by an SAE approved third party.

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    Watts To Boiler Horsepower

    Formula to convert watts to boiler horsepower:

    Since boiler horsepower is equal to 9,809.5 watts, the formula to find boiler horsepower is the power in watts divided by 9,809.5.

    For example,

    Watts and horsepower are both units used to measure power. Keep reading to learn more about each unit of measure.

    Gross Or Net Horsepower:

    Mechanical Horsepower (hp) Calculator

    Gross or Net horsepower is measured where the crankshaft of any engine is located. It does not take any sort of transmission losses. It produces rankings in closer alignment with the power that is being created by the engine because it is in reality organized and sold. However, it is the actual measurement of output created by the engines at the flywheel. It will be measured only when the engine is not fitted in the vehicle.

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    Measuring The Horsepower Of An Engine

    Direct Measurement

    In principle, we could measure the horsepower of an engine the same way that Watt defined it: see how much weight the engine can lift a specified distance in a given time.

    The animation to the right illustrates for a motorcycle engine. A pulley is mounted on the crankshaft, and turns with the engine. A weight is hanging from the pulley by a rope, and the engine lifts the weight at a constant speed. The weight has a magnitude of F and the pulley has a radius of r.

    In practice, this method is very hard to use since a real engine turns at thousands of revolutions per minute.

    Indirect Measurement

    The way the measurement of the horsepower of an engine is typically performed is similar to the illustration to the right. The pulley mounted to the crankshaft of the engine is in contact with another pulley via a high-friction material between them. A weight is hung from the second pulley, and its mass is adjusted so that it is stationary.

    The Mechanical Equivalent of Heat experiment in the laboratory uses a very similar technique. The Guide Sheet for the experiment is here.

    The engine shown in these animations is from a Suzuki SV650 motorcycle. The image is used by permission. The original site is:…sv650_info.htm

    In the Direct Measurment above, after one revolution of the engine, the work done by it is the circumference of the pulley times the force:

    After the engine has made \n revolutions, the work done is:

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    Introduction To Simulation Physics#

    The backbone of train simulation physics is the simple equation, F=MA . Acceleration is a measure of how quickly you are gaining or losing speed. Read more on accceleration here.

    We want to find the acceleration of the train, and we can use algebra to rearrange F=MA, making it Acceleration = Force/Mass. So to find the acceleration we need to know the force acting on the train and the mass of the train. The mass is easy to find. The force…not so much.

    Not familiar with F=MA?

    If you are not already familiar with the basics of F=MA, please read more on that here. There are some excellent practice problems to get you comfortable with Newton’s second law on that page as well.

    How To Calculate Water Pump Horsepower

    Work and Power Calculations for a Water Pump: physics problem

    This article was co-authored by wikiHow Staff. Our trained team of editors and researchers validate articles for accuracy and comprehensiveness. wikiHow’s Content Management Team carefully monitors the work from our editorial staff to ensure that each article is backed by trusted research and meets our high quality standards.wikiHow marks an article as reader-approved once it receives enough positive feedback. This article received 15 testimonials and 86% of readers who voted found it helpful, earning it our reader-approved status. This article has been viewed 449,635 times.Learn more…

    A pump is a basic but important mechanical device that supplies the force to move fluid at a specific flow rate. Like any device that does work , its effectiveness is measured in power. Although watts and kilowatts are more common units of power measurement, horsepower is still commonly used for high-output electrical devices in the United States. In this context, 1 horsepower is equal to 746 watts.

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    What Does It Mean To Convert Hp To Amps

    Hp stands for the horsepower – the unit of, well, power. Similarly, the amps represent the amperage, which refers to the electric current measured in amperes.

    Whenever you face the challenge of converting horsepowers to amps, you are about to estimate the output current from a device with awell-defined power.

    Analogically, if you try to convert amps to hp, you should evaluate the power knowing the output current.

    Great! As we’ve just established what the hp to amps calculation is, it’s high time asking how to do the task.

    How To Calculate Hp Knowing Flywheel Weight

    So I’ve seen a guy on Youtube that has an RC nitro engine. He attached a quite big flywheel of known weight to its output, and then by measuring the time that it takes to reach max rpm he was able to calculate the HP and torque. Now, I want to know the math behind it. I guess that it has something to do with inertia but I’m not a physics genius. I suspect that he also knows the diameter of the flywheel. So if for example we have a flywheel that is 50cm in diameter and weighs 5kg and the time it takes to rev it up to 8k rpm is 10s then how much hp would it be? If someone is willing to explain it to me I’ll be happy.

    To my knowledge, it is not possible to calculate the engine’s power from the information that you provided. Several things are missing:

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