What is Horsepower: Definition and 90 Discussions

Horsepower (hp) is a unit of measurement of power, or the rate at which work is done, usually in reference to the output of engines or motors. There are many different standards and types of horsepower. Two common definitions used today are the mechanical horsepower (or imperial horsepower), which is about 745.7 watts and the metric horsepower, which is approximately 735.5 watts.
The term was adopted in the late 18th century by Scottish engineer James Watt to compare the output of steam engines with the power of draft horses. It was later expanded to include the output power of other types of piston engines, as well as turbines, electric motors and other machinery. The definition of the unit varied among geographical regions. Most countries now use the SI unit watt for measurement of power. With the implementation of the EU Directive 80/181/EEC on 1 January 2010, the use of horsepower in the EU is permitted only as a supplementary unit.

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  1. P

    I Prony brake calculation help (for determining engine horsepower)

    I need some help here. I'm trying to determine how to use the numbers I'm getting for my pony break to determine horsepower at the axle of my engine. Right now I'm getting a reading of six pounds of torque, 4 in off of the center line of the axle at a rate of 30 rpms. Can someone help me...
  2. T

    Power, Rpm, Torque - Horsepower increase for my small engine

    Hello all, the short story is, I am basically trying to get the same ( or a little more) “power” out of a larger lawn mower type gas engine ( vertical shaft) as one of the largest (120 ish cc) chainsaws ( ref the Stihl MS 880 or newer 881 at approx 10-12k rpm and 9 Hp) The parameters are : a...
  3. L

    DIY Simple analog engine dynamometer -- How to do it?

    Hi, I have to measure the HP of a small engine at the crankshaft. The only usable things are. A dinamometer A brake disk An rpm meter The brake caliper is floating so when we apply de load it pull the dinamometer. The rpm meter show the revolution during the load apply. It can works? How I...
  4. bagasme

    Why Isn't Horsepower an SI Unit, Despite Its Popularity?

    When we talk about engines on automotive industry (cars, motorbikes, trucks, etc.), we often refer the power produced by such engines by horsepower. But when we talk about electricity, the power is measured in kilowatts. Despite the former case is highly popular, why isn't horsepower considered...
  5. ar2x7ar

    How to Calculate This Horsepower from a flywheel?

    I have a flywheel (150 Kg, Diameter-18", RPM) How I Calculate Horsepower from These information. I am working on a project Thank you physicsforums
  6. S

    Calculating required horsepower

    My attempt at the solution goes as follows: power = work / time power = (distance * force) / time power = (2640 ft * 2000 lb) / 6 seconds = 880000 ft lb / sec horsepower = 880000 ft lb/sec / 550 ft lb/sec = 1600 hp however i do not know if this is correct
  7. Chincha40

    B Hp/Kw required to move 1.5L/m of diesel fuel at 17.2 Bar?

    How much Hp/Kw required to move 1.5L/m of Diesel fuel at 17.2 Bar? Please note this is for a real life problem.
  8. T

    Regarding the measurement of horsepower

    I teach aerodynamics. One horsepower is 550 lbs moved one foot in one second. My question is this. Does that assume that the 550 lbs is being lifted vertically against gravity? As opposed to moving, say, a 550 lb chunk of concrete across a floor. And if so, does the gravity value of...
  9. Arjun Singh

    KiloNewton/Pound foot of thrust into Horsepower units

    Hi, I am currently studying aviation engine outputs and to make my study linear in comparative analysis with standard Automotive engines I need some expert help. Can anyone help me drive precise equations to convert: 1. Engine thrust in Kilo Newton into Horse Power and Watts 2. Engine thrust in...
  10. FreeBob

    Calculating equivalent horsepower for a jet engine

    Trying to remember some basics. I know the thrust of a jet engine. I'm thinking about equivalent HP. I can establish HP at a given speed, but what about while accelerating? I will display my ignorance here :( Power for static, non accelerating flight: Power = [Thrust x Airspeed] Thrust...
  11. FreeBob

    What is the Career of a Retired Chief Technologist in Servo/Mech R&D?

    BSME Missouri University of Science and Technology (was University of MO at Rolla) '78 Retired after 32 year career in disk drives Chief Technologist managed about 150 electrical, mechanical and computer science engineers developing servo mechanics for hard disk drives Two boys, one graduating...
  12. O

    Calculate Horsepower from a flywheel

    I have a flywheel (not connected to an engine, just on a shaft and bearings, so assuming zero resistance), that weights 60 lbs, 18" wide, at 3200 RPM's. How can I calculate horsepower, brake, or torque? Working on a project, Thank you, Larry
  13. shintashi

    Automotive Can Flying Hypercars be Modified to Fly?

    Recently the Bugatti Chiron set a record of some sort for rapidly accelerating to 249 mph and then dropping back down. The engine is something to the effect of 1500 horsepower and the vehicle isn't terribly heavy. Old Airplanes had engines below 400 horsepower and ultra lights can be far less...
  14. Nissan Jon

    How Much HP Needed to Reach 300 MPH in a Nissan 350z?

    Salutations, I specialize in high performance solutions for Nissan vehicles. I've recently gotten into the top speed Texas Standing Mile competitions. The current champion is using a Ford GT with unknown power to set the record at 274 MPH from a still launch; I want to beat his record. I...
  15. P

    How Horsepower is equal to 550 ft lb/s ?

    How did James Watt found out that one horsepower is equal to 550 ft lb/s ? There must be some sort of derivation or something that he did.Can anyone show me that derivation.
  16. D

    Convert horsepower to duck power

    Okay, so maybe this is the wrong forum. I'm here as a last resort, I've been on 4Chan and ask websites for three hours just looking for ideas, or God willing, some real data. I've been tasked by a friend to convert horse power into duck power. It sounded easy at first but I'm stuck. I've barely...
  17. Oannes

    Finding Horsepower given Pressure, Diameter, and Distance

    Homework Statement When gas is burned in a cylinder of an engine it creates a high pressure that pushes a piston. If the pressure is 100psi and it moves a 3 inch in diameter piston a distance of 5cm every .1 seconds. How much horsepower does this action produce?Homework Equations Pressure =...
  18. Z

    New Definition derivative for Horsepower

    There has been SO much talk of HP and HP vs torque, it can make your head spin. I've been trying to help with some clarification for those that seem to be very confused of the physics and concepts that i came up with a new "definition" to augment what is commonly read as the definition of HP...
  19. Pao44445

    Calculating Horsepower Needed to Lift 150 kg for 20 m in 10 min

    Homework Statement Lifting a box (150 kg) up for 20 meters in 10 minutes, how much horsepower needed? Homework Equations 1 Watts = 1 Joule/sec 1 Horsepower = 746 Watts The Attempt at a Solution I've figured this out but I got a very low horsepower :( about 0.065 hp, does it correct?
  20. R

    Calculating Minimum Horsepower Needed for Object Movement

    Homework Statement If weight x distance over time equals work done. Work done divided by time will give me work done over time foot pounds. Foot pounds can be converted to horsepower. So I should be able to find minimum horse power needed to push a known weight a known distance in a known time...
  21. S

    Does Horsepower or Torque Determine a Vehicle's Acceleration?

    My dad and I are having a debate about HP and torque. He thinks that a 400hp diesel with 800ft lbs of torque will have more power and out pull and have better acceleration than a gas engine with 400 hp andf say 300 ftlbs of torque. As I understand it, the relationship between HP and torque is as...
  22. W

    Horsepower in inches per second?

    Hello Wizards! O.K. I know that 1 horsepower is generated by moving 300 lbs 100 feet in one minute. The question I seem unable to answer is... How many horsepower is generated by moving 19 lbs 1-1/2 inches in 1 second? Help please ( my brain is exploding ) Best Regards, Bill
  23. C

    What formula defines the power (i.e. horsepower) of gravity?

    What is the calculation that shows how much power is required to offset gravity? Gravity force is defined with units of kg.m.s-2. How to convert that to Joule.s-1? I am talking in the context of theoretical physics, not practical engineering like using a rocket or helicopter. But BTW could...
  24. T

    Best acceleration torque or horsepower?

    i want to ask that in same gear which is true? a)car accelerates best at the max torque rpm or b)car accelerates best at the max horse power rpm which is true and why we talk these conditions at same gear thanks
  25. A

    Why do F1 car have high horsepower rather than torque?

    I've heard the analogy that a high torque car is like a bodybuilder, it is powerful but slow. And a high horsepower car is like a sprint runner, it runs fast, but not as powerful. Considering other factors constant. if each tries to ride a bicycle to a certain speed, and the runner is given a...
  26. Ankhen

    Tesla magnetic field holding force and horsepower to remove magnet

    Hi. Is it posible to make an equation to solve this: How many horsepower does it takes to remove a magnet with the force of 1 tesla, from a piece of metal. ? The surface of the magnet and the surface of metal is the same size. I gues the angel of witch the magnet is being pulled affects the...
  27. M

    Automotive Horsepower and torque question

    Hi all nice site just trying to figure something out about how low RPM and high torque vs high RPM low torque for moving a load. This is a subject I have been trying to understand and it seems I am missing something, Ok take you have a 238 HP Mack Semi that makes 1100 ft pounds of torque...
  28. M

    What would affect horsepower more: speed or mass?

    I was wondering which would cause the horsepower to increase and why would it be that one.
  29. L

    Force, Horsepower and Acceleration logic?

    hi guys, Im not a science student but wanted help in understanding a few fundamentals. Here is where i have learned till please correct me if i am wrong. is it correct if i state, "If you can lift 74.6kgs off the ground to a height of 1m in 1sec you have power = 1hp?" i say that cause i read...
  30. mootz

    Horsepower needed to lift 600 lb load, w/8 motors

    Good day Geniuses. im building a drone prototype for an agricultural project. approx. weight will be 600 lbs, using my own 8 rotor design. trying to determine rotor size and motor power required to fly such a device at 30 feet. would also be interested to determine an approximate wind speed...
  31. D

    Horsepower vs hill gradient problem

    So, I have a car I'm tuning using a road dyno software. This software basically uses the gear ratio of the car, it's total weight, and the speed it moves the RPM to determine it's power output (HP and Torque) In order to use this software a flat road is needed. That works well and is very...
  32. K

    Calculate Horsepower to Velocity for Model Train Control

    Hello, I'm building a model train control system, and would like to use real world values and physics to control the trains. I have these specifications about each model of train, and would like to know how I could relate given HP to velocity or Δacceleration. Given Values are located here...
  33. K

    Automotive Can the horsepower of a car be given per cylinder ?

    say a car has 400 horsepower at the fly wheel with a V8. can you divide 400 by 8 to give 50 hp of power transmitted by each piston ? Just for a rough estimate, does it even come close to the real power transmitted by each piston or is way far off and wrong ? The reason why I think of this way...
  34. M

    Calculating Power Output of a Car Accelerating from 0 to 27 m/s in 60 seconds

    Homework Statement A 1200 kg car accelerates from 0 to 27 m/s in 60 seconds. a) What is the power outage from the engine in watts? b) What is the power outage from the engine in horsepower? Homework Equations 1/2 mgy=v 1 horsepower=746 Watts The Attempt at a Solution My...
  35. H

    Need help figuring required horsepower of electric motor

    I have built a conveyor system but still need to power it. It is not a conveyor belt, but rather a trolley of sorts for moving materials up to the second floor. It runs parallel to stairs for about 17 or 18 feet in my garage at an angle of apx 38°. It needs to be able to move at least 500 lbs...
  36. S

    Question about horsepower for car

    I am wondering how much horsepower would be needed, or generated (not sure which term is right), if a diesel car with a 250HP motor, and weighs 3,500 pounds, is going up a slight incline (maybe 2 or 3 degrees) averaging 20 mph? Thanks.
  37. J

    Calculating the horsepower for a motor

    Homework Statement This is not really a homework question, it is a question for a project I am working on. So I have a heavy rod that is 1.4 m long and I want to get a motor to rotate it (I would like to see if this is even plausible). I calculated the moment of inertia for this rod to be 75.2...
  38. K

    Why do diesel engines produce less power than gasoline engines?

    Hello all; I have been thinking about this for some time and searching through the internet for it but couldn't get a satisfactory answer for it, so i decided to ask this to you. Here is my question: If diesel fuel has more energy in it than gasoline does and if diesel engines are more...
  39. A

    Need to calculate mass to potential horsepower

    I need to calculate how a mass (of an unknown weight) suspended on a pulley and shaft, what would be the weight in lbs (or Kg for that matter) to give me a 50 hp output using a series of gear reducers going from less than 1 rpm to the input shaft and a final output rpm of 1850. the configuration...
  40. R

    Does this horsepower for this car seem like the right value?

    For a lab in physics where we have to go through an enormous process to calculate the drag coefficient, I am trying to figure out if one of the values I got along the way makes sense so that I don't continue with bad data. I gathered time and speed deceleration data and drove a 2002 Honda...
  41. G

    How to calculate needed horsepower for radial travel

    I have a conveyor that travels radially. I need to calculate the HP needed to move it. It works on a concrete slab. The Motor RPM is 1750 and a reducer of 180:1. Any help would be great. Thanks
  42. S

    Gear Train horsepower calculation

    I am designing a gear train for my basic mechanisms class that consists of three shafts. The input horsepower is 10 and rpm is 1750. I calculated the torque of the first shaft to be 360 but I am not sure if the horsepower stays the same throughout the whole train or not. The first shaft has a...
  43. J

    Finding work with given horsepower

    Homework Statement If one ferretpower (fp, made-up unit) is equal to 0.0312 hp, and an electric motor puts out 2.75 x 10^5 fp, how high (in meters) can it lift a crate that has a mass of 2.75 slugs in 5 s?Homework Equations P = W/t W = mgh 1 hp = 745.7 watts 1 slug = 14.59 kgThe Attempt at a...
  44. W

    Relating speed and engine horsepower of a ship to water resistance

    Homework Statement The aircraft carrier John F. Kennedy has mass 7.4*10^7kg. When its engines are developing their full power of 280000 hp, the John F. Kennedy travels at its top speed of 35 knots. If 70% of the power output of the engines is applied to pushing the ship through the water, what...
  45. S

    Inductive generators, what is their output compared to their horsepower rating

    Let say I have a 3 phase ac motor rated at 40 hp. Now I'd like to be able to convert this to act as a single phase induction generator (I hear is possible but I don't know much about it). driven by an ICE at around 1800 rpm. What would its power output be in kilowatts. Or more importantly...
  46. D

    Aircraft engine horsepower display

    I am trying to design an on-board horsepower display for an experimental aircraft. The parameters that determine engine power are RPM, manifold pressure, altitude, temperature and mixture. Each of these parameters is currently monitored and displayed individually in the airplane and the...
  47. C

    Estimating vehicle horsepower and torque

    Given the following instantaneous parameters and constants... Known: d = air density = 1.24 Cr = rolling resistance coeffecient = 0.015 FA = frontal area = 1.48 Cd = drag coefficient = 0.29F G = gravity (mps2) = 9.80665 pi = 3.1415926 m = vehicle mass (Kg) = 1542 DL = drivetrain loss = .2 V...
  48. C

    Dozer Engine Torque and Horsepower Calculations

    I have been given a project at work to find the number of dozers needed to push a certain volume of material in a certain amount of time. My issue comes with the actual horsepower of the dozers. We run D10T, D11R, D11R CD, and D11T Cat "track-type tractors". So from what I am thinking, I want to...
  49. T

    Looking to calculate horsepower by mearuring the change in rpm

    as the title states I am looking to solve how to calculate power (horsepower) by measuring the change in rpm over a few seconds. torque will be kept constant at 200lbs/ft. hp= (torque x rpm) / 5252 since torque will be held constant it reduces to: hp= C x rpm where C is 200/5252 so...
  50. H

    Automotive How performance car parts influence torque vs horsepower?

    I am currently majoring in mechanical engineering at Texas A&M after having completed my associates degree in automotive technology (4.0gpa) while i'v been fixing cars at Firestone Autocare. Its odd that i rarely find anyone who knows a thing about the physics of energy efficiency and the...