Horsepower is NOT how fast you hit the wall. Torque is NOT how far you take the wall with you

Last Sunday I published a video where I tried to make a very down to earth and visual explanation of Horsepower and Torque to help anyone confused by the two concepts wrap their head around them. And apparently it worked for a lot of people as I received a lot of positive comments and feedback. This made me extremely happy and I am very grateful for all the comments and feedback. But I also received a very high number of comments containing this phrase: "Horsepower is how fast you hit the wall. Torque is how far you take the wall with you". I decided to make this follow up video in hopes of clearing away the misconceptions around this and similar explanations of horsepower and torque that are very frequently used in the car community. I believe that reinforcing these explanations as facts isn't a very good idea as they are ultimately misleading and will serve as a poor knowledge foundation for someone who doesn't understand the concepts.

NOTE: In the video I said that we will come back to the first part of the definition "horsepower is how fast you hit the wall" but I didn't actually come back to it. I apologize for that. This video was completely unscripted and made ad-hoc as I was getting overwhelmed with the sea of identical comments. What I wanted to say was this: If our two cars from the same example have everything identical except the amount of horsepower, then yes, the one with more horsepower will be capable of hitting the wall faster. But if everything else is identical (max rpm) than the car with more horsepower also must have more torque. This means that you could just as well say that Torque is how fast you hit the wall.

The gist of the video is that horsepower is not how fast you hit the wall. That's speed. And horsepower is only one factor influencing speed. There are also aerodynamics, gear ratios and much more. Torque is definitely not how far you take the wall. That's momentum. If we imagine two cars, one with 1000 Nm of Torque and the other with 100 Nm of Torque, with everything else on the cars being absolutely the same, these two cars will carry the wall the absolutely same distance if they both have the same mass and hit the wall at the same velocity. This is because momentum is only influenced by mass and velocity.

Basically the main problem with all the quasi definitions of horsepower and torque are that they're trying to correlate horsepower and torque to acceleration and speed. This doesn't work because acceleration and speed are complex concepts influenced by multiple factors so these "definitions" need like 5 disclaimers to have an even remove chance of working, and a definition that needs disclaimers isn't very good at doing it's job. The only definition that really doesn't need a disclaimer is that torque is a rotational force and horsepower is the rate of that force. This definition underlines another key problem of the other "definitions" and that's their separation of torque and horsepower. Trying to draw distinction between the two concepts only creates confusion because horsepower and torque are in fact inherently connected. Horsepower is torque times rpm. Horsepower is very much dependent on torque. The more torque you have the higher the chances that you'll also have more horsepower.

If you must have a car and a wall here's a better use of a car and a wall. Torque determines whether you can move the wall from a standstill. Horsepower determines how fast you can keep pushing the wall. This is still far from perfect and refutable but it's a better definition as it isolates torque and horsepower a bit better and takes acceleration and velocity and vehicle mass out of the equation.

Original artwork characters in the thumbnail are from POWeeeeeRRRRRRRRRRrrrrRRRRRRRR by Sadyna

A special thank you to my patrons:
Daniel
Peter Della Flora
Daniel Morgan
William
Richard Caldwell
Pepe
Brian Durning
Andrew Ruud
Brian Alvarez
Holset90

#d4a #horsepower #torque

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[stevenash]

Torque is the rotational equivalent of linear force/Horsepower is the rate at which work is done. You explained it very well in your electric motor vid.

[atlasnovalis]

"Speed doesn't kill. It's suddenly becoming stationary, that's what gets you." - Some Old Brit.

[Mxbuthead]

This man is such a legend, the car community needs to treasure him

[johnbarron]

I'm always amused to see whole cartridges flying rather than just the bullet. But in any case, this analysis is well-done and pretty darn accurate.

[realrururu]

Torque is how hard something is spinning. RPM is how fast something is spinning. Horsepower is just the combination of these two things to get the job done.



Something spinning with a lot of torque but with very low RPM will be very slow but very hard to stop (like a tank cannon). This thing could get the job done but it will take forever, so it has low horsepower. An example would be the motor for an elevator, it's moving a lot of mass but it does it slowly.
Something spinning with a high RPM but with a little torque will be very fast but very easy to stop (like a handheld fan). This thing might not even get the job done because it is so weak and easy to stop, so it has low horsepower. An example would be a desk fan, it's moving mass quickly but it's not a lot of mass, it's just air.
Something spinning with a lot of torque and a high RPM will be very fast and very hard to stop. This thing gets the job done AND does it fast, so it has high horsepower. An example of this would be a sports car engine, it's moving a lot of mass really quickly.

In the context of everyday driving:

Whenever you shift gears you're telling your car how much torque vs RPM you want at the wheels in that moment.
When you're in first gear, you're telling your car "I need you to push harder, not faster." Since it takes a lot of force to push a car from a stationary poisition, you start it off in first gear. When you're on the road and want to go faster, you shift to a higher gear, telling your car "You don't need to push as hard, just push faster". You can see how an engine with a lot of torque is more useful to a semi-truck than an engine with less torque but capable of a higher top speed.

[blkmage]

Thank you. I've heard this statement waaaay too many times.

[cipher]

You literally explained this shit in the simplest, best way possible and some people still manage to fuck it up...
My disappointment is boundless --_--
[Also thanx for bothering to upload another video regarding this <3]

[kamilzmich]

Thanks. I grew tired of explaining this to people, now I can just link this video! haha

[williambrewer]

The visual with the bullet still in the casing was funny

[DENZLLA]

Great explanation and clarification! I never liked the the expression 'horsepower is how hard you hit the wall, torque is how far you take it!!' Your definitions are visually clearer and easier to understand. WELL DONE 👍

[michaelblacktree]

If people are having trouble with torque vs power, then torque multiplication via gearing is REALLY going to throw them for a loop! 😛

[Macintoshiba]

10:02
This moment was priceless to me. I didn't know for sure, what Horsepower is. I knew what torque was. I figured it would be something along the lines of "the frequency at which torque is applied". Finally, I have clarification, and no longer have to guess in the dark.
Thank you!

[DanielFrost]

Kudos for correction people who just can't see what they say are wrong/incorrect.
In fact, my brother gave me the same explanation because he "learned if on the internet". He got mad when corrected.

[oseh]

Thank you for doing this... the amount of people in comment sections who think they are above the laws of physics and don’t understand basic physics is very annoying

[t_c]

I think a good way to portray this is to use the concept of a motor as a wrench instead of a spinning object. You take put more torque into a large wrench and the numbers will be far higher (the big motor is just a large circular wrench in essence) but when you try to spin that giant thing fast, its hard. On the other hand if you have a tiny wrench, you dont get much turning power, but you can spin the ever living hell out of it quite easily.

[welltell.]

Well after watching this video i feel much smarter. I finally understand the concept. Thank you.

[stevenash]

Your way of explaining electro/mechanical/hydraulic theories is an artform.

[tuftistump]

Awesome video dude, the last video was so clear to understand bhp and torque its hard to believe that people could even make any sense of "bhp is how fast you hit the wall, and torque is how far you make it move" it literally makes no sense, how ever adding the fact that hp = torque x rpm has just made the first video even more clear, awesome videos.

[hege]

I just found out this channel and it's great to see that Engineering Explained is not the only one explaining automotive mechanics from a physics standpoint.

[genesismachina]

Another video victory for common sense and actual facts. Keep up the great work.