Impact force -- Airsoft versus paintball pellets

[LT72884]

Ok, here is a small back story:

I love both airsoft and paintball. Airsoft, for those who may not know what it is, is a sport where you shoot 6mm plastic bbs at each other. The bbs have differnt masses to them.. .20g, .25g .28, and .32 are common masses.

When i first started last year, i was told that airsoft does not hurt nearly as bad as paintball.

I am not believing that because they both equally hurt to me. Eapecially lasts night airsoft game at night time in a close quarters filed with 40 rounds per second.

So this got me thinking last night. If KE=mv2/2, then yes paintball has higher KE for sure, anout 12times more with these conditions

Paintball is .68 inches or 17.2mm explodes on impact

Airsoft bb is 6mm solid plastic

KEpaint=(3.3g)(300fps)2/2 or using 91.5m/s for v instead of 300feet/s

We get 13814.21

Now

KEbb=(.20g)(400fps)2/2 or 122 m/s

We get 1488.4

If i wanted to see what velocities i needed the bb to fly at to hit with same energy as a paintball, i set the two equations equal to each other and solve for v

(.20)(v)2/2=13814

Ok, so what my main point is, how do i find out how much force each one is hitting my skin?

F=ma but i don't know acceleration and I am not sure i jave enough info to use projectile motion equations to solve for (a).

I know that F=dP/dt or F=(Pf-Pi)/time. I am just not seeing how to calculate impact force and which one hits harder, especially when i change the mass of the bb and or the velocity?

Thank you much for this help. This is not a school question. Just personal curiousity:)

 

[lokibear0803]

Here's a useful reference: http://hyperphysics.phy-astr.gsu.edu/hbase/impulse.html. That is useful if you know how deeply the impact of paintball or BB pushes into your body, e.g. you can start with an assumption of 100% of the projectile's diameter (so 17.2mm or 6mm, right?). Read the part about the duck and the aircraft, and use the equation for "impulse" to derive force = mass * (delta-v/delta-t). Calculate time t using depth of impact / velocity. Also you might want to check your math on the KE calculations, but you don't necessarily need KE here. Regardless of using KE, be sure to convert grams to kilograms (and mm to meters, or cm if you use the calculator at end of duck story). I get approximately 500N for the 0.2g BB with diameter (length) of 6mm traveling at 122 m/s and pushing in with a depth of impact equal to its diameter. Let me know if my calculations are right! In either event, I believe this is the right direction for your problem.

 

[sophiecentaur]

It's mainly the kinetic energy of the projectile that counts. This link gives a list of energies of bb and paint ball at different speeds.
See also this link and this link..
Google rules for this sort of question. you can read faster than you can Q and A.

 

[lokibear0803]

@sophiecentaur -- OP is asking for force, not KE, if I'm reading correctly. And yes, agreed that google rules here :-)

@LT72884 -- to try further clarification, the acceleration you want is the negative acceleration (assuming positive is in direction of BB) experienced by the BB when it slows from it's initial velocity to zero.

 

[LT72884]

Here's a useful reference: http://hyperphysics.phy-astr.gsu.edu/hbase/impulse.html. That is useful if you know how deeply the impact of paintball or BB pushes into your body, e.g. you can start with an assumption of 100% of the projectile's diameter (so 17.2mm or 6mm, right?). Read the part about the duck and the aircraft, and use the equation for "impulse" to derive force = mass * (delta-v/delta-t). Calculate time t using depth of impact / velocity. Also you might want to check your math on the KE calculations, but you don't necessarily need KE here. Regardless of using KE, be sure to convert grams to kilograms (and mm to meters, or cm if you use the calculator at end of duck story). I get approximately 500N for the 0.2g BB with diameter (length) of 6mm traveling at 122 m/s and pushing in with a depth of impact equal to its diameter. Let me know if my calculations are right! In either event, I believe this is the right direction for your problem.

Ke=(m(v^2))/2 please help me see where my calculation is messed up:)

Thanks for the link as well. I will read that next. I have a feeling I am going to feel bad for the duck haha.

 

[sophiecentaur]

OP is asking for force, not KE,

That question is not answerable because it depends on the object / person who is hit. As I said, it is the KE that counts and not "the force". Which force and at what point in the impact?
Hitting someone with the term "acceleration" when they ask a question like the OP may not be very helpful, however 'correct' the term may be.
Search PF for "Force of Impact"'"Force of a punch" etc. you will find many discussions in which the first thing that gets sorted out is the most appropriate and relevant question.

 

[LT72884]

Ohh mass is in kg for ke not g. Thanks. Also, i know some of this might be difficult to answer, I am just looking for approxamets.

I just want to know how much impact a bb hits me with vs a paintball becauce my nerves and pain receptors tell me its fells just as painfull as the other.

To me a paintball should hurt more because its more massive, but i tell you what, those bbs last night hurt like a mother father haha

 

[LT72884]

That question is not answerable because it depends on the object / person who is hit. As I said, it is the KE that counts and not "the force". Which force and at what point in the impact?
Hitting someone with the term "acceleration" when they ask a question like the OP may not be very helpful, however 'correct' the term may be.
Search PF for "Force of Impact"'"Force of a punch" etc. you will find many discussions in which the first thing that gets sorted out is the most appropriate and relevant question.

Yeah maybe my nerves are shot and all impacts feel the same. Bb, paintball,golfball,baseball.. i do have odd nerves haha

I know when it comes to shooting real steeln balistics is done off of impact energy, but does a higher impact energy mean more of a "punch" or "kick" to the body and therefor more pain

 

[sophiecentaur]

I know when it comes to shooting real steeln balistics is done off of impact energy, but does a higher impact energy mean more of a "punch" or "kick" to the body and therefor more pain

As you say, it's much more complicated than that. It may have to be resolved by a series of tests. Volunteers line up here.

 

[LT72884]

But what kind of tests haha. I mean it might just be up to each individual what hits harder. To you maybe airsoft feels more painful than paintball but to lokibear maybe paint hits harder haha.

Im still going to look at all the links. I do have volunters who are willing to do this. So would i need a high speed camera to see impact depth of each?

 

[LT72884]

By the way. Thanks to all of you for voicing in. All my classes, each question could be answered in a two hour class period haha

But i felt like i could never get answers to my real life questions:) then i found you guys.

 

[sophiecentaur]

it might just be up to each individual what hits harder.

Exactly. The mechanical aspect of this is probably not the major one.

 

[LT72884]

Exactly. The mechanical aspect of this is probably not the major one.

Well, i just shot my wife and she can't tell a difference she said.

Ok, so I am totally going to change the concept. What if i dropped a 300lb rock onto a house? How much force is that rock exerting onto the roof of the house? For all purposes, the roof is really strong and does not cave in.

I like the rock example better. It seems like it actually has a solution.

Thanks.

Anyone can chime in on this one. The paintball one is on the shelf haha

 

[sophiecentaur]

Ok, so I am totally going to change the concept. What if i dropped a 300lb rock onto a house? How much force is that rock exerting onto the roof of the house? For all purposes, the roof is really strong and does not cave in.

Even that question is not sufficient for a proper answer.
Just consider this. You jump off your roof onto the concrete driveway. You jump the same distance onto loose sand. You jump onto a safety mattress. The resulting damage to you would be because of the Force on you - ok? So the Forces would all be different, despite the same height and the fact that you end up stationary.
If you gently rest your 300lb rock then the Force can be predicted with certainty (=300lb - I am not too familiar with Imperial Units but I guess that's right as lb is Weight which is a force) Dropping from any height adds a lot of complication and you cannot know the answer because it depends entirely on the construction of the roof - even if the roof does not break the forces can be wildly different, depending.
This conversation is going the same way as countless others have gone. You are insisting (reasonably enough for everyday conversation) that your question is quite reasonable. If you want a sensible answer which is based on Physics (and Engineering) you have to re-state it or accept advice as to what would be a better (answerable) question. See if there are any other responses to this or ask on another (technical / Engineering) forum and you can expect a similar reply.
For an answer to your bb question, the answer is just as elusive as for your rock / roof question. You would need to specify the experimental details much more if you want to know the peak value of the forces involved.

 

[sophiecentaur]

Well, i just shot my wife and she can't tell a difference she said.

How brutal!

 

[LT72884]

Even that question is not sufficient for a proper answer.
Just consider this. You jump off your roof onto the concrete driveway. You jump the same distance onto loose sand. You jump onto a safety mattress. The resulting damage to you would be because of the Force on you - ok? So the Forces would all be different, despite the same height and the fact that you end up stationary.
If you gently rest your 300lb rock then the Force can be predicted with certainty (=300lb - I am not too familiar with Imperial Units but I guess that's right as lb is Weight which is a force) Dropping from any height adds a lot of complication and you cannot know the answer because it depends entirely on the construction of the roof - even if the roof does not break the forces can be wildly different, depending.
This conversation is going the same way as countless others have gone. You are insisting (reasonably enough for everyday conversation) that your question is quite reasonable. If you want a sensible answer which is based on Physics (and Engineering) you have to re-state it or accept advice as to what would be a better (answerable) question. See if there are any other responses to this or ask on another (technical / Engineering) forum and you can expect a similar reply.
For an answer to your bb question, the answer is just as elusive as for your rock / roof question. You would need to specify the experimental details much more if you want to know the peak value of the forces involved.

Well, let's not turn this into a never ending thread. I am a full time engineering student currently and these are the questions that jump into my head when studying dynamics and strwgths. But they are real world problems not found in a book which makes it more difficult haha.

As per your last reply, i greatly appreciate it:) i do not want this to be one of "those" threads, just merly wanting to understand things better haha.

 

[Shadow89]

I don't think there is a way to scientifically measure pain, science the pain receptors and neurological responses of humans can vary.

However, for a rough estimate, I would still use kinetic energy, and simply subtract the amount needed to create a certain splatter pattern from the paintball.

Also; when you use the nonmetric grain unit, you should write 20gr. Not 20g. I strongly doubt you got twenty gram bullets in your bb-gun.

 

[LT72884]

Sorry. I thought i put .20g as in 2/10 of a gram:) thanks for the reply.
For some reason, airsoft bbs are measured in grams

 

[Shadow89]

Sorry. I thought i put .20g as in 2/10 of a gram:) thanks for the reply.
For some reason, airsoft bbs are measured in grams

My apologies. I see now that it was a clever use of decimals, and it totally makes sense.

As I was saying; some kinetic energy is consumed for the plastic deformation of the paintball and content. After subtracting this energy you know how much is absorbed by human body parts. Then compare to the plastic bbs. I hope that helps and good luck.

 

[LT72884]

My apologies. I see now that it was a clever use of decimals, and it totally makes sense.

As I was saying; some kinetic energy is consumed for the plastic deformation of the paintball and content. After subtracting this energy you know how much is absorbed by human body parts. Then compare to the plastic bbs. I hope that helps and good luck.

That does help thank you:)

I was thinking along these lines and hopefully i can come up with some good results. But my feelings are that i can do the mechanics, but peoples response to pain is the key factor