New Definition derivative for Horsepower

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Discussion Overview

The discussion revolves around the definition of horsepower (HP) and its relationship with torque, particularly in the context of automotive performance. Participants explore various interpretations of HP, its role in vehicle acceleration, and the implications of these definitions in practical scenarios.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants propose a new definition of horsepower as "a measure of a vehicle's capacity to accelerate," suggesting that this perspective clarifies common misconceptions about HP and torque.
  • Others argue that existing definitions of horsepower are sufficient and that the proposed definition is too vague, noting that acceleration does not directly correlate with horsepower in a straightforward manner.
  • Several participants emphasize the importance of using kilowatts instead of horsepower, arguing that the term "horsepower" can lead to confusion and misinterpretation of its meaning.
  • One participant highlights the distinction between torque and horsepower, asserting that they are fundamentally different physical quantities that cannot be directly compared without considering angular velocity.
  • Another viewpoint suggests that the relationship between power and torque is not a simple one, indicating that factors such as traction and wheel stand resistance also play significant roles in vehicle acceleration.
  • Some participants express frustration with the common narrative that torque is a measurement while horsepower is a calculation, arguing that both are physical quantities that can be used to analyze performance from different perspectives.
  • There is a discussion about the implications of gear ratios and driveline efficiency on the relationship between horsepower and torque, with some noting that lower-torque engines may require more gear reduction, complicating their performance characteristics.

Areas of Agreement / Disagreement

Participants generally do not reach a consensus on the definition of horsepower or its relationship with torque. Multiple competing views remain, with some advocating for a new definition while others defend traditional interpretations.

Contextual Notes

Some participants mention the need for clarity in definitions and the potential for misunderstanding among those who use these terms incorrectly. There are also references to the limitations of existing definitions and the complexities involved in comparing horsepower and torque.

  • #31
rootone said:
I an sure we have now better definitions of 'amount of work done'. than estimating how many typical sized draft horses are required to transport some number of sacks of grain to the local brewery.

Tradition is pretty strong in industry. We still measure engine speeds in rev/minute, even though rev/second at least uses an SI unit for time, and rad/sec would be more proper still. But how many people would understand that?

At least we know that 1 horsepower = 550 ft-lbf/sec, and we can convert easily enough to watts. Even the Germans have a metric horsepower, the Pferdestärke, or PS DIN. Maybe people just still relate to a comparison to the capability of a horse.
 
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  • #32
rootone said:
I an sure we have now better definitions of 'amount of work done'. than estimating how many typical sized draft horses are required to transport some number of sacks of grain to the local brewery.
Actually, its not the amount of work done... that would be energy. HP-seconds, (a unit measure of work) Joules.. etc... Hp or Power, would be the rate that work is being done. ;) This is why, in the spirit of the defintinon (or one of the defnintions) of energy . "a body's capacity to do work"
HP, could be a car's (or vehicle) capacity to accelerate at any speed.

Randy Beikmann said:
Tradition is pretty strong in industry. We still measure engine speeds in rev/minute, even though rev/second at least uses an SI unit for time, and rad/sec would be more proper still. But how many people would understand that?

At least we know that 1 horsepower = 550 ft-lbf/sec, and we can convert easily enough to watts. Even the Germans have a metric horsepower, the Pferdestärke, or PS DIN. Maybe people just still relate to a comparison to the capability of a horse.
i think its way deeper than that, its really about power's relationship and measure of accelerative forces (translational or rotational) . that rate of doing work, gets commonly confused with quantity of work done. with the right gearing, a bunch of turtles can bring those same sacks to the brewery, but it might take them a while. ;)
 
  • #33
zanick said:
i think its way deeper than that, its really about power's relationship and measure of accelerative forces (translational or rotational) . that rate of doing work, gets commonly confused with quantity of work done. with the right gearing, a bunch of turtles can bring those same sacks to the brewery, but it might take them a while. ;)

Well, you can see why my 17-chapter book doesn't tackle the subject of power until Chapter 14. It isn't nearly as obvious as torque is.

But remember that power can be used for a lot more than acceleration of mass. That's just one aspect of it.
 

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