# How Do You Convert PSI Into Pounds Of Pressure?



## Kane (Aug 10, 2004)

I found from somewhere that the average punch force for a heavyweight boxer is over 700 PSI however Mike Tyson has achieved 900 PSI. 

Now from here, how do you convert the PSI into pounds of pressure? I heard from somewhere I think (I dont remember where) that you divide it by two to convert PSI of a punch. That means 700/2= 350 pounds of pressure. Now for Mike Tysons punch I think its 900/2= 450 pounds of pressure.

Now did I do that wrong? If I did the wrong 
procedure, how do you convert PSI of a punch into pounds of pressure? Thanks!


----------



## Taimishu (Aug 10, 2004)

Correct me if I am wrong but I always thought that PSI stood for POUNDS per SQUARE INCH so no conversion needed.

David


----------



## satans.barber (Aug 10, 2004)

Taimishu is correct, PSI is a measure of pressure (hence tyre pressure at 30PSI or whatever...)

Ian.


----------



## oldnewbie (Aug 10, 2004)

Okay I'll bite....


Pound per square inch.... Tyson can do 900psi... so

Let's say that his fist (the surface that hits you) is 2 inches high and 3.5 inches wide... 2 x 3.5 = 7 square inches.... I would then multiply 900 times 7 sq inches and say that his punch can produce 6300 pounds of fource.....or would you divide and get 128.57 pounds of fource......


oh crap.... now I gotta open a book.............


----------



## OULobo (Aug 10, 2004)

Whoo-hoo, physics lesson. I thought I would never use this stuff. 

As stated, PSI is Pounds per Square Inch. Pressure by definition is a force applied over an area. The force is measured in pounds and the area is measured in square inches. There is no such thing as just pounds of pressure. There is however such a thing as pounds of force (lbf) which is actually (and here's where it gets confusing) 32.174 foot pounds of mass by a squared second (lbm ft / s^2) or mass times acceleration. Oldnewbie was right in taking the approximate contact area of Tyson's fist, and you multiply the PSI value by that area to get lbsf or pounds of force, but remember that force has little to do with impact or knocking someone out. It is pressure that counts. Dropping a distance of two feet and landing evenly flat on your back will do little or no damage, because the force is dispersed across the entire area of your body, but dropping the same two feet on a pencil pointed at you will puncture your skin because all the force is focused on the pencil tip.


----------



## Taimishu (Aug 10, 2004)

OULobo said:
			
		

> Whoo-hoo, physics lesson. I thought I would never use this stuff.
> 
> As stated, PSI is Pounds per Square Inch. Pressure by definition is a force applied over an area. The force is measured in pounds and the area is measured in square inches. There is no such thing as just pounds of pressure. There is however such a thing as pounds of force (lbf) which is actually (and here's where it gets confusing) 32.174 foot pounds of mass by a squared second (lbm ft / s^2) or mass times acceleration. Oldnewbie was right in taking the approximate contact area of Tyson's fist, and you multiply the PSI value by that area to get lbsf or pounds of force, but remember that force has little to do with impact or knocking someone out. It is pressure that counts. Dropping two feet evenly flat on your back will do little or no damage, because the force is dispersed across the entire area of your body, but dropping the same two feet on a pencil pointed at you will puncture your skin because all the force is focused on the pencil tip.


Phew

As he said

David


----------



## bignick (Aug 10, 2004)

yeah...add up 900 lbs for every square inch he he hits you with...it's it a big boxing glove...lets say it's 4-5 inches....

do the math...

4 inches x 900 pounds/inch = ouch

just simple math


----------



## Kane (Aug 10, 2004)

So 700PSI or 900PSI can only be achieved with boxing gloves? So without boxing gloves, what PSI would the punch be with your bare-handed punch? Or was those numbers (700PSI and 900PSI) achieved without gloves? Is it possible to get those numbers without gloves? Again, would it be high or lower?

Also, if it is called pounds of force what are the pounds of force of 700PSI or 900 PSI in a punch? I was sure that they could measure the pounds of force with punches (and maybe kicks which would probably be more). 

They have measured lion or tiger bites, and that is at 1,000 pounds of force. Lions and tigers bite with their four canines and those canines are about one inch away meaning that their PSI should be 4,000PSI.

I am assuming if there is someway to measure a cat bite, I'm sure a human punch even without gloves could be measured.


----------



## tmanifold (Aug 10, 2004)

It goes the other way. If tyson hits 1000 psi (round figures) and the size of his glove is 10 inches squared then he woud hit with 100 pound per 10 inches squared. If his hand was 5 inches sqaure then he would hit with 200 pounds per 5 inches squared. Which do you think would cause more damage.

Tony


----------



## Eldritch Knight (Aug 10, 2004)

Keep in mind that PSI is only concerned with the measurment of the size of Tyson's hand, or rather the impact surface across his knuckles. The PSI that he can apply stems from his body, and thus is retained only by objects part of the same system. His gloves, in this case, are not firmly affixed to his arm, and thus serve as a padding, dispersing the force, not amplifying it.


----------



## MA-Caver (Aug 11, 2004)

Eldritch Knight said:
			
		

> Keep in mind that PSI is only concerned with the measurment of the size of Tyson's hand, or rather the impact surface across his knuckles. The PSI that he can apply stems from his body, and thus is retained only by objects part of the same system. His gloves, in this case, are not firmly affixed to his arm, and thus serve as a padding, dispersing the force, not amplifying it.


Yeah, but try to explain that to all the guys he's knocked out during the height of his career... Those gloves probably are what kept his fist from going through their heads and out the other-side... I watched (on tee-vee) the guy fight and wondered about standing against him...for a brief moment I'd wish I had a bazooka with an armor-piercing round. The man puts his entire body force and emotional content into his blows...combined with the speed and intensity of his attacks... no wonder he was so lethal as a fighter. Just too bad that he was less human than his opponents like Hollifield.


----------



## OULobo (Aug 11, 2004)

Again, this one is a little onlg winded, but physics can be hard to grasp. 



			
				Kane said:
			
		

> So 700PSI or 900PSI can only be achieved with boxing gloves? So without boxing gloves, what PSI would the punch be with your bare-handed punch? Or was those numbers (700PSI and 900PSI) achieved without gloves? Is it possible to get those numbers without gloves? Again, would it be high or lower?



Essentially, the gloves lower the applied force/pressure/impact by making the striking surface larger, thereby dispersing the force over a greater area; more area means less force per unit of area. Without the goves the striking surface is smaller, so a greater force is applied to each unit of area. If Mr. Tyson is operating at a prime and constant effort (assumption), then theoretically the force he generates will always be the same no matter what the striking surface. Changing the striking surface from glove to fist to whatever, will change the pressure or applied force (felt impact or damage), but the force generated with always be the same. 



			
				Kane said:
			
		

> also, if it is called pounds of force what are the pounds of force of 700PSI or 900 PSI in a punch? I was sure that they could measure the pounds of force with punches (and maybe kicks which would probably be more).



You can only determine the pounds of force from a PSI (pressure) amount if you know the striking surface area. This we have to assume, unless you can get Mr. Tyson to measure or let you measure his fist or glove or whatever he hits you with. In this equation you have three variables (force generated, striking surface area and pressure). If you have two of them you can solve for the third. 



			
				Kane said:
			
		

> They have measured lion or tiger bites, and that is at 1,000 pounds of force. Lions and tigers bite with their four canines and those canines are about one inch away meaning that their PSI should be 4,000PSI.
> 
> I am assuming if there is someway to measure a cat bite, I'm sure a human punch even without gloves could be measured.



I think they have measured force generated by the animal's jaw. This would be in pounds of force, but again that number doesn't mean much unless you know what area it is applied across. In this case it is a very small area of the four first contacting teeth (canines), but as the canines sink in, the dynamics of the system change. After the bite is sunk, all the teeth are in contact and so the force is applied over a much greater area, thereby lessening the pressure. If there is 4000PSI of jaw force, there are four initial teeth making contact and they each have a one quarter square inch of surface area (striking surface), then each tooth shows a 4000 PSI pressure initially (because it will change when they sink in and the rest of the teeth come into play). The equation is  F / n / A = P (F=force=jaw force generated, n=# of teeth in contact, A=striking surface area=tooth striking surface, P=pressure=felt impact), 4000/4/.25=P=4000. 

In terms of a human punch, the equation is the same. F/n/A=P (one fist, so n=1 and can be dropped). If Tyson generates 900 PSI (=P) with a punch that is 7 in^2 (=A) with a glove (assumed) and he punches level and true to that assumed surface of his fist, then his generated force would be 6300 pounds of force (=F). If the same punch was leveled without a glove and we assume that the lack of glove reduces the striking surface of the punch by 2 in^2, then the ungloved punch would be 1260 PSI, a differance of 360 PSI. Theoretically, that's about 360 PSI more pressure or impact if he punched without a glove. 

None of this takes into account the absorbing effect of the glove padding, which reduces force by using it to compress the padding in the glove before the force can be transfered through the padding to the target.


----------



## Ronin Moose (Aug 11, 2004)

To take it one step further, can someone proffer an estimate of the force of Tyson's *bite*, as compared to the average Pit Bull Terrier?

Just curious..........


----------

