# Sticky  Horsepower vs Torque Relevance and Explanation Attempt!



## Bandem (Aug 29, 2012)

Not as easy as you may think. I can't tell you how many people I know who have the mindset of:

"Power is just a calculated value and therefore unimportant, your torque is what's important because its what actually accelerates you" or
"My muscle car has only 200hp, but a billion lb-ft of torque and therefore is as fast as car with more power"

And most of all, what drives me nuts is the extremely common confusion when people think torque is the same thing as work since both involve force and distance...Torque has nothing to do with work or energy. A lot of people don't realize that and its probably in the roots of that misconception.


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## AutoGuy (Jan 30, 2014)

That is a pretty thorough explanation on the difference between torque and horsepower. Really explains why horsepower is more important than torque in acceleration. Nicely done.


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## Leo-RochesterMI (Mar 3, 2014)

Great texts here:

Let's not forget though that the application also plays a role in this discussion. 

If one wants to scream the engine at max power, power is everything that maters. However, high torque will keep the driving experience "effortless" in normal everyday driving. 

If you can afford it, you want to have the most power capable, large engine (torque), and the most sophisticated large transmission (more gears) that money can buy. That's what many cars are labelled as a delight to drive in any conditions (eg, Aston Martin 12 cyl., except race track), and others recognized as quite laborious to drive (eg, Ferrari V8, anywhere but in the track).

Not very difficult, just a matter of money and/or application.



Leo-RochesterMI
2010 30ixDrive Black/Black


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## cridge (Mar 6, 2014)

*Reminds me of that old adage ...*

Understeer is when you hit the wall with the front of the car.

Oversteer is when you hit the wall with the rear of the car.

Horsepower is how fast you hit the wall.

Torque is how far you take the wall with you


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## dsx724 (Jun 21, 2010)

cridge said:


> Understeer is when you hit the wall with the front of the car.
> 
> Oversteer is when you hit the wall with the rear of the car.
> 
> ...


loled at the last one.


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## Fish23 (Apr 24, 2012)

dsx724 said:


> loled at the last one.


Me too. Well done........

Sent from BimmerApp mobile app


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## nicobmwlife (Nov 22, 2014)

thank you for writting this. Solid points!


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## nicobmwlife (Nov 22, 2014)

cridge said:


> Understeer is when you hit the wall with the front of the car.
> 
> Oversteer is when you hit the wall with the rear of the car.
> 
> ...


Killin it !!


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## sinahb (Jun 13, 2014)

Wow, just wow. All that detail! thanks a lot


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## Damon44 (Oct 28, 2014)

As if I was taking Physics again in the 70's. Excellent definitions of basic principles. Wonderful reference material. Thank you.


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## Phil2204 (Oct 10, 2015)

A well written and thorough explanation. Many thanks for taking the time and sharing!!


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## jlbjr (Jul 22, 2015)

This sounded interesting until you made the statement about holding the flywheel of the engine. No way that is right. JMO.


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## Morgan444 (Sep 14, 2016)

"An engine, even the most powerful around are much weaker than many realize. An average grown human can take the flywheel of most street engines in use today and hold it in place even if the engine is operating at maximum throttle."
What???
I'd love to see someone hold the flywheel of even a small engine when just turned over on the starter motor. 
There is a very direct relationship between torque and horsepower. The formula originally posted is the single thing in the OP that is in any way relevant:
Horsepower = (Torque x RPMs) / 5252
The constant of 5252 has a complex calculation behind it that is probably not important to this discussion. The thing to understand is that horsepower is calculated from torque which in turn is physically measured on a dynamometer. But importantly, nothing about this formula has anything to do with the acceleration of the vehicle or the speed of the propshaft. It has only to do with the speed of the engine (RPM) and the torque produced by the engine at specific engine speeds.
The reason why a car cannot accelerate well at low speed in 3rd gear is because the engine RPM at that road speed in that gear is too low to produce torque. This is a characteristic of the engine design.
Just look at a torque curve graph - this is not rocket science.
When you see a car being run on a "rolling road" (dynamometer), do you think they're measuring horsepower? They aren't, they're measuring torque. The horsepower rating is derived from the torque measured.
"If power is merely a calculation . . . ." It's not a case of "if". It IS merely a calculation.
Actually, there is so much wrong with the OP, I'm astonished that this has been given "sticky" status.


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## zombimmered540i (Nov 8, 2016)

I'm glad I read this. Someone above me in the comments said, and im paraphrasing, "a noob that reads this wont gain in knowledge, and will have more questions at the end." I have to say, at 44 I have the amount of time it took me to read this vested in the hp vs Nm's. Aside from 9th grade science and the usual math classes. I now can say, without a doubt, that I understnd what the two units of measurement mean, and why gearing is so important. For the first time in my life i own a car that I want to spend my time and money on. I havent so much as washed a car in 12 years. Til a few months ago. Now i have a kick ass E34 on jack stands in my garage, front end dismantled, and parts in the mail. What does this all mean? I dont have the foggiest. But I do know that if tbis is the quality of info i will find on here, Im gonna love this forum as much as I do my Zombimmer. I tend to ramble, sorry. Great explanation. cant wait to school a few chevy owners. thanx for the knowledge. sincerely


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## NBA Jam (Mar 26, 2017)

The way I try to think about it:

Torque - What you need to move
Horsepower - How fast you use your torque 

Consider two extremes:

- Imagine a massive truck trying to move a space shuttle. It moves very, very slow, but it can pull the shuttle. This is similar to something with high torque, low horsepower: its engine doesn't spin very fast, but it produces a lot of power for each revolution.

- Imagine a small car trying to move a space shuttle. The engine spins very fast, but it can never move the shuttle. This is similar to high horsepower, low torque: it can use the torque quicky, but because there's not enough of it, neither the car nor the shuttle go anywhere.

Torque is what does the work to move you, horsepower is how fast it does the work.

Of course these analogies aren't precisely how reality is, but it's a way to wrap your brain around it.


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## Morgan444 (Sep 14, 2016)

NBA Jam said:


> The way I try to think about it:
> 
> Torque - What you need to move
> Horsepower - How fast you use your torque
> ...


Fundamentally you are correct but . . . .

As I said in my post above, there is a very direct relationship between torque and horsepower. What this means generally speaking is that an engine developing high horsepower will not have low torque and conversely, high torque will not result in low horsepower.

And if your analogy with the massive truck is taken to the next step, no matter how much torque or horsepower the giant truck has, if it is not geared correctly it will not be able to do any work. E.g. if a heavy vehicle (say a Freightliner Argosy with 560hp, 1,850 lb-ft torque) tries to pull off in top gear, it will not get away, even with no load at all. The high gearing will simply not allow it. But in super low gear it is capable of moving well over 100 tons from stationary.

The useful expression is "Torque gets you up to speed, horsepower allows you to stay there"

Cheers
Andre


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## CMann (Sep 2, 2014)

*Thank you*

That was a great explanation and helped me wrap my head around a few things I struggled to understand in the past.


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## Beamer Schemer (Jun 1, 2016)

cridge said:


> Understeer is when you hit the wall with the front of the car.
> 
> Oversteer is when you hit the wall with the rear of the car.
> 
> ...


 That is bloody amusing so I am going to steal it.:thumbup:


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## bimmergazm (Jan 3, 2018)

When i remapped my e39 530dA i increased torque only from 420 to 490 because i dont want to break automatic transmission, but most off all that tork only works about to 3k rpm, after that it doesn't matter, because power depends from horse power So my remapped 258 hp is really enough.:thumbup:


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## LeeL (Mar 25, 2021)

HP is how fast you can go at Given conditions . Torque is how fast you can make thing get going from a stand still.

So, when you are running at 70mph, how fast you can get to 100mph would be HP as you don’t need too much to get going but a linear climb of efforts. However, a drag race from 0-60 mph would rely on Torque and traction. The higher and earlier the Torque @RPM, and better traction is the faster you can get things going.

Electric Vehicle has amazing torque because they are electric that has burst power and Electric motors, but they often struggles on achieving HP. However, with how advanced the transmission are engineered nowadays, the EV most of the time will win in both Torque and HP specs. This is why Hybrid and Hyper vehicles are like the best of both worlds....but they are complicated to fix as there are multiple systems and that makes them being a very complicated cluster to govern over


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## targaone (May 10, 2018)

Its very technical but the more math the less understanding among most people. 
My abilty to understand comes from the different engines and machines I use. 
My cessna 310 with 3 blade props has the ability to climb out heavy and reaches top engine speed using a reasonable amount of fuel . 
My f350 v10 can pull 17000 pounds up a steep hill and maintain 70 mph , but cant out accelerate a 200 hp bmw straight six even unloaded. 
My 1800 pound 20 hp kohler twin boxer air cooled tractor can easily pull a 10 thousand pound boat. The torque allows some serious pulling but acceleration is about nill. 
My motorcycle is a moto guzzi with a 22 pound flywheel. It feels very very powerful up to about 45 mph. After that it feels very very slow as its a low hp engine.


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## LadyDiYer (Aug 13, 2021)

Nice explanation


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## Goobies818 (Aug 4, 2021)

Bandem said:


> Credit: Carstechinfo.com


I haven't read the entire thread...but i have my own metaphor on how i describe Torque/HP.

Torque is a measurement of how MUCH work/force an engine can do
HP is a measurement of how FAST an engine can work

To continue...let's say you have an office desk. This office desk in bolted into the ground...no matter what you do...this desk won't move an inch (think of Thor's Hammer scene in Avengers Age of Ultron)

You can take an NFL defensive lineman and have him push up with all his force against said desk...he's working and there's force being exerted on the desk...but he ain't going anwhere...but that force being exerted..

On the flip side...you can have that same desk...but now being pushed by the team's cheerleader...both the lineman and cheerleader are getting the same result (no movement) but you know the lineman is exerting substantially more force)

Now...let's take the same example,, but put the desk on rollerskates...here the lineman can get the desk moving along...and so can the cheerleader...but obviously...the lineman will move faster, accelerate faster and prob have a higher top speed...hope that helps...it worked for me a few years ago to better understand


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## G80M4 (Dec 9, 2021)

it's very simple. 
torque (at a given rpm, as it changes with rpm) is how much force (grunt) the engine can produce at that rpm.
power (at a given rpm) is how much effort (work) the engine is producing at a given rpm.
(bench press once = torque, bench press 100 times = power)
(in car physics speak, torque = acceleration, power = top speed)

but even that makes little sense - let's convert it to driver's feelings in a car: 
torque = defines ability to move a load at a given rpm
power = acceleration available at a given speed

what is important depends on what you are after. if you want your car to just move, torque is the thing that moves it. if you want your car to accelerate, the power gives you reference for the speed ceiling of how much acceleration is available at a given speed.

an 18 wheeler truck has 2000ft lb torque and 200 hp.
a bmw has 300ft lb torque and 300hp
a bmw with 300ft lb torque and 600hp.

the truck will move whatever load, put a house on it and it will move up the hill. but it won't accelerate.
the bmw won't move a house. but take away the house, it will accelerate well until you get to 60mph and the acceleration to be had will gradually decrease.
the bmw with 600hp will accelerate well until you hit 120mph (assuming no wind resistance) when it will cease accelerating well.

don't forget gearing in the gearbox is a torque multiplier. 1st gear will multiply the torque at any given rpm, 5th gear will divide (reduce) the torque at any given rpm.


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## denzil73 (Dec 5, 2021)

BHP is really just a marketing term cos 800hp sounds better than 400hp but it's the torque that makes HP as HP is just torque x RPM. Hence why a CAT deisel can be producing 1000lbft at 1500rpm but far less HP is made due to how it's calculated mathematically.

As torque generally drops off whilst the HP is still increasing after say 5000rpm then this is why your vehicle will slow down if you suddenly have to drive up a hill. Sure there's gearing involved but in a nutshell the engine is no longer producing enough torque to push the vehicle up the hill.

This is also why modern turbos can flatten the torque curve so by say 1500rpm it can be at max torque and hold that flat all the way to 5000rpm. This makes for a much more driveable vehicle as the torque is always availbale for daily driving and pulls the vehicle along more effortlessly.

Vice versa old turbo vehicles of the 90s would have bugger all torque until the turbo starts the spool up and then the torque suddenly takes off and due to the way HP is calculated then the HP starts increasing quickly too.

So what everyone really wants is to see the torque curve of the vehicle they want to buy and if this torque curve doesn't start increasing quickly by 1200rpm and by 2500rpm being at a decent level for the size of the vehicle and hold this at least until 5000rpm then it may drive OK but quite likely to feel rather sluggish.

So everyone needs to stop thinking about BHP and start thinking in terms of Torque


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## G80M4 (Dec 9, 2021)

denzil73 said:


> So everyone needs to stop thinking about BHP and start thinking in terms of Torque


i think you should sell your bmw and buy a truck  [since you said it has 1000lbft torque]


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## denzil73 (Dec 5, 2021)

kiwinz said:


> i think you should sell your bmw and buy a truck  [since you said it has 1000lbft torque]


I don't own a truck. I was just using it as an example.


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## scuderiazane (Jan 19, 2021)

Horsepower is indeed used a lot for marketing and chest-thumping. Nothing wrong with that, but driving enjoyment is what's important to me. I don't race or do track days, so I really don't care how I'm doing against a clock or another driver. I get enjoyment from driving my 540i, C43 and Alfa Spider, but all for completely different reasons. This is an interesting discussion tho, so I'll sit back and watch.


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## denzil73 (Dec 5, 2021)

scuderiazane said:


> Horsepower is indeed used a lot for marketing and chest-thumping. Nothing wrong with that, but driving enjoyment is what's important to me. I don't race or do track days, so I really don't care how I'm doing against a clock or another driver. I get enjoyment from driving my 540i, C43 and Alfa Spider, but all for completely different reasons. This is an interesting discussion tho, so I'll sit back and watch.


Yea, a vehicle isn't just about power n torque. It's the feeling it gives you when driven. My daily is a 2003 Ford Focus 1.8L manual. It's comfy yet handles pretty well in the twisty stuff but could do with a bit more get and go but overall is a nice drive compared to other newer and more expensive vehicles I've driven.

My, new to me, 2001 E46 320Ci wafts along ever so nicely and it's so quiet inside that it can make me feel a bit sleepy. It's a little bit pokey when you put your foot down but the M54 is just such a smooth drive


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## lgr122 (Aug 8, 2012)

HP vs. Torque, they are helping each other, not alternatives.

Many big trucks out there have 400-500HP, and they are pulling 60tons of load. You could try same with your 1000HP BMW or Supra, and you're just smoking your tires till your car die.

Truck which has 500HP also has 2800Nm of torque.

You can't beat cubic inches like you americans would say. Turbo or supercharger can help though.


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## Doug Huffman (Apr 25, 2015)

Buy horsepower, drive torque.

No one would ever guess that VW TDI had only 90 Hp.


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## lgr122 (Aug 8, 2012)

Doug Huffman said:


> Buy horsepower, drive torque.
> 
> No one would ever guess that VW TDI had only 90 Hp.


My e91 diesel has only 7HP more than earlier e46, but it has 150Nm more torque. It's different animal.

Winter time it's not any bit faster, because tire is limiting factor. Summertime this low power thingie can go, when it's time to go. 2000-3000rpm...

I still miss sound of my M54 though, that sound close to redline was so beautiful...

(I'm aware this 325d is basically same car like 330d, just programming can give me more at once)


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## scuderiazane (Jan 19, 2021)

This all dovetails into the issue of 0-60 times. To me it getting to the point of ridiculousness. I'm sure someone would enjoy a car with a 0-60 time of 2.0 seconds that needs computer driver aids to keep it one the road, but I wonder how long people with keep buying such cars.


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## Autoputzer (Mar 16, 2014)

O.k. Let me take a crack at this...

Short definition:

*Torque is the ability of an engine to twist the crankshaft and therefore to twist the input shaft to the transmission. Torque translates into the ability of a vehicle to accelerate.

Power is the ability of an engine to apply torque while the crankshaft and input shaft to the transmission are rotating at a specific rotational speed. Power translates into the ability of a vehicle to accelerate at a specific speed.*


Long explanation:

*Energy is mechanically transferred by applying a force over a distance, where the force and the movement of the object or surface to which the force is applied are in the same direction. Here are some examples:*

In an internal combustion engine, high-pressure combustion gasses push against a moving piston during the combustion stroke, transferring mechanical energy to the piston. The force of the high-pressure combustion gasses acting on the face of the piston and the piston's travel are in the same direction.

When you draw back an arrow, you are applying a force toward the bowstring. The bowstring moves in the same direction that you pull it. That transfers energy to the bow, via the bowstring. Energy is stored in the bent bow. When you release the bowstring, the bowstring applies a force onto the arrow, and that force applied to the arrow is in the same direction as the arrow is traveling. That transfers energy to the arrow.

Wind pushes the blades of a windmill. The portion of the wind force that is in the direction of the blade motion transfers energy from the wind to the blade.

Flicking a hockey puck applies a force to the puck which is in same the direction that the puck travels. That transfers energy from the hockey stick (and hockey player) to the puck. The energy then resides in the puck as kinetic energy (1/2 m v^2).

Energy is transferred to a spring by compressing or extending it. The force to compress or extend the spring is in the same direction as the compression or extension.

If you lift a bucket of water up from the bottom of a well with a rope, the rope applies a force to the bucket which is in the same direction as the bucket's motion.

*Mechanical energy transfer, and therefore energy have the units of force x distance, e.g. pound-feet or newton-meters. A newton-meter of energy is a joule.

Power is the rate at which (how fast) energy is produced or transferred. The units of power are force x distance / time which is also force x velocity, e. g. pounds-feet/second or newton-meters/ second. A newton-meter/second is a watt.*

Consider a bucket of water of weight W hanging above a well on a rope from a pully of radius “a.” Now consider a crank on the pully shaft with the crank arm length of “b.”










The bucket of water of weight W is lifted by applying a force F to the crank handle. The force F is applied to the crank handle perpendicular to the crank arm of length b (feet).

Torque is a twisting “moment” and is equal to the force times the arm length. Applying a force F to the crank handle on a crank arm of length b will result in a torque of value (Fb). Similarly, the water bucket of weight W hanging from a pully of radius a is exerting an opposing torque of (Wa). If (Fb) is just slightly greater than (Wa), the bucket of water will be lifted.

*One horsepower is defined as 550 pound-feet / second. That means that if you are transferring or producing 550 pound-feet of energy every second you are transferring or producing one horsepower.*

If you push with a horizontal force of 55 pounds on the back of a car in neutral for ten feet, you have transferred 550 pound-feet of energy from you to the car. If it takes you ten seconds to push the car ten feet, you have transferred energy at an average rate of 55 pound feet / second, or 0.1 horsepower.

Now again consider that crank lifting the water bucket.

The circumference of a circle is 2π times the radius.

If you exert the force F on the crank for one complete revolution, the application point of force F (the crank handle) will move (2πb) as shown by the dashed green circle in the diagram. Since energy is force x distance, you have transferred (F2πb) of energy from you to the pully and then from the pully to the bucket of water. (The bucket of water now has more energy because it is higher and might also be moving at some non-zero velocity.)

Now consider the pully rotating at c revolutions per minute (c RPM) with a force F applied to the crank handle. That would mean that the crank handle is moving a distance of (c2πb) every minute or (c2πb/60) every second. So, the velocity of the point where the force F is applied, the crank handle, is (c2πb/60) in feet/second if (b) is measured in feet. Since power is force x velocity, the power (rate of energy transfer) would be (Fc2πb/60) or (Fb)(c)(2π/60), where (Fb) is the torque applied to the crank shaft and (c) is RPM.

*So, the power is equal to torque x RPM x (2π/60).*

Since one horsepower is defined as 550 pound-feet / second,

*Horsepower = Torque x RPM x (2 π) / (60 x 550), where torque is in pound-feet.*

So, my 535i which produces a maximum torque of 300 pound-feet at 5000 RPM would be producing:

(300)(5000) (2 π)/(60 x 550) horsepower, or 285.6 horsepower at 5000 RPM

An N55's torque is pretty much flat at 300 pound-feet up to just above 5200 RPM. 300 pound-feet of torque at 5200 RPM results in 298 horsepower.


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## lgr122 (Aug 8, 2012)

Autoputzer said:


> O.k. Let me take a crack at this...
> 
> Short definition:
> 
> ...


Very complete explination indeed.
But if you try to explain someone, who never did before, then you need the simple version. As simple as you can get.


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## Autoputzer (Mar 16, 2014)

lgr122 said:


> Very complete explination indeed.
> But if you try to explain someone, who never did before, then you need the simple version. As simple as you can get.


A complex concept can be explained with simplicity, but the explanation has to be long. The trick is to present small simple concepts where each new concept builds on previous concepts.


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## Here2Learn (11 mo ago)

This is the most beautiful breakdown ever.


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## lgr122 (Aug 8, 2012)

Autoputzer said:


> A complex concept can be explained with simplicity, but the explanation has to be long. The trick is to present small simple concepts where each new concept builds on previous concepts.


Still requires that other one listen.
Big challenge for science is the people, who ignore and don't listen to the truth.


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## Autoputzer (Mar 16, 2014)

lgr122 said:


> Still requires that other one listen.
> Big challenge for science is the people, who ignore and don't listen to the truth.


People need to have information fed to them in small portions that can be swallowed and digested. If you do that you can convince people of something, instead of just telling people of something.


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## lgr122 (Aug 8, 2012)

Maybe I would go different way.

Let's say, there are 4 heavy bags, which small guy can lift only one at time. Very big guy can lift them all together (that's TORQUE). Then, job is to take all 4 bags to 2nd floor. If small guy can run so fast that he can get 4 bags to 2nd floor in the same time like very big guy does, then they have equal POWER. But it doesn't remove the fact that only one of them can move 4 bags at the same time.


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