Example of Inertia - why you should use heavier bb's.

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Example of Inertia - why you should use heavier bb's.

Post by Guges Mk3 » Sun Jul 11, 2010 3:34 pm

Many of you always want better range and accuracy...you always ask for upgrades to make your gun more accurate and shoot further.

Well, the simple answer to both is a heavier bb.

Now for those of you that shoot .20's, you say...but a .20g bb has a higher muzzle velocity then a .25g bb. It's on average ~50fps higher. To those of you that say that...I say, you are absolutely, positively correct!

But, at 10 yards, I'll say the .20g bb will be traveling as fast as the .25g bb. But, you ask...how can this be?!

Well...its a physical principle called Inertia!

Inertia - Physics - The tendency of a body to resist acceleration; the tendency of a body at rest to remain at rest or of a body in straight line motion to stay in motion in a straight line unless acted on by an outside force.

And the last example is an airsoft bb.

Which ties into Newton's Three Laws of Motion:

Newton's laws of motion
The three laws proposed by Sir Isaac Newton concerning relations between force, motion, acceleration, mass, and inertia. These laws form the basis of classical mechanics and were elemental in solidifying the concepts of force, mass, and inertia.

Newton's first law states that a body at rest will remain at rest, and a body in motion will remain in motion with a constant velocity, unless acted upon by a force. This law is also called the law of inertia.

Newton's second law states that a force acting on a body is equal to the acceleration of that body times its mass. Expressed mathematically, F = ma, where F is the force in Newtons, m is the mass of the body in kilograms, and a is the acceleration in meters per second per second.

Newton's third law states that for every action there is an equal and opposite reaction. Thus, if one body exerts a force F on a second body, the first body also undergoes a force of the same strength but in the opposite direction. This law lies behind the design of rocket propulsion, in which matter forced out of a burner at high speeds creates an equal force driving the rocket forward.

And the key here is MASS, the heavier the bb...the more air resistance it take to slow it down. Thus while the .25g bb leaves the barrel slower then the .20g bb. The .25g bb will travel further because its mass is higher and it takes longer for air resistance to slow it down.

Now, I am about to give you a real life example.

If you take a pitcher in baseball and you hand him a baseball. He winds up and with his perfect motion he throws a 100 mph fastball. He does this over and over again and just hits strikes. Plain, simple for strike fast balls. The baseball leaves his hand at about 102mph and hits the catchers glove at about 100mph.

Now, take away that baseball and give him a whiffle ball the size of a baseball and have him throw it with the same perfect motion he uses for baseballs. How many of you can already see whats going to happen? His velocity is not going to be 100mph at the catchers glove. The whiffle ball may even leave the pitchers hand at 125 mph, but at 60 feet what his velocity? 40 mph, 30 mph, 20 mph? How many will say it may not even make it to the plate, except maybe on a bounce or two? How is his accuracy? Pretty bad, no?

Well the "same" thing happens in airsoft. Lighter bb's have worse range and worse accuracy.

So...shoot a heavier bb for better range and accuracy!

Questions?
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Re: Example of Inertia - why you should use heavier bb's.

Post by uRizen » Sun Jul 11, 2010 6:33 pm

I have always wanted to set a chrono out at different ranges and see what the velocity of differently weighted BBs works out to. Theoretically you're right, heavier BBs will retain more inertia, in practical experience I haven't noticed much of a difference when switching between .20g and .25g rounds, the .25gs win out just a bit in accuracy, range seems about the same.

I'm a cheap bastard so getting 4000 rounds compared to 2500 rounds for the same price wins over any minor accuracy differences in my book. :D
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Re: Example of Inertia - why you should use heavier bb's.

Post by Guges Mk3 » Sun Jul 11, 2010 7:56 pm

Accuracy by volume...a lot of these "China" bb's are coming out in 1KG bags.

Which means 5000 for .20 and 4000 for .25.
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Re: Example of Inertia - why you should use heavier bb's.

Post by lord_coz » Sun Jul 11, 2010 11:22 pm

um... hulk smash?

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Re: Example of Inertia - why you should use heavier bb's.

Post by Mailman » Mon Jul 12, 2010 2:56 am

wow, all that I can say is thanks next time I buy bb's I will remember 25g
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Re: Example of Inertia - why you should use heavier bb's.

Post by Gill » Mon Jul 12, 2010 3:32 am

But what about the force of gravity? Doesn't that have anything to do with accuracy in airsoft? Because obviously gravity will act different on a .40 than a .20.
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Re: Example of Inertia - why you should use heavier bb's.

Post by Guges Mk3 » Mon Jul 12, 2010 7:54 am

Gill wrote:But what about the force of gravity? Doesn't that have anything to do with accuracy in airsoft? Because obviously gravity will act different on a .40 than a .20.
Remember this Italian dude called Galileo? He went up the Leaning Tower of Pisa and dropped two objects of different weights off the tower and they both hit the ground at the same time? Well him going up the tower is debatable, but he did do the experiment on an incline...same results.

Now another factor that I will touch is the Bernoulli Effect...damn...what's with those Italians!

This is the back spin that a hop-up puts on a bb, it changes the properties of a bb from projectile to a lifting body, a wing.
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Re: Example of Inertia - why you should use heavier bb's.

Post by Gill » Mon Jul 12, 2010 9:10 am

Guges Mk3 wrote: Remember this Italian dude called Galileo? He went up the Leaning Tower of Pisa and dropped two objects of different weights off the tower and they both hit the ground at the same time? Well him going up the tower is debatable, but he did do the experiment on an incline...same results.
Oh yeah, I didn't even think about that. What I was really thinking about was that your example of the pitcher throwing the baseball. What if he had a baseball made out of solid steel (same mass more weight)? He obviously wouldn't reach the plate with a straight fastball unless he was roided out of his mind. Does that equate to the loss of fps when BB weight goes up? Elaborate please. :D
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Re: Example of Inertia - why you should use heavier bb's.

Post by Viper » Mon Jul 12, 2010 9:31 am

Gill wrote:What if he had a baseball made out of solid steel (same mass more weight)?
Umm, what? You do realize that weight is just the measure of the force due to gravity against an object. As Guges said earlier, F = ma (mass times acceleration). Acceleration in the case of weight is just gravity, g, which is a constant (that's not strictly true as it depends upon distance from the center of the Earth, and latitude, but for all intents and purposes, it is a constant). As such, weight is directly and linearly proportional to mass. So, "same mass more weight" isn't physically possible. Sorry.

Two objects will fall at the same rate (starting with zero velocity in the Y-axis), regardless of weight. If two objects (a baseball and steel ball in your case) have the same horizontal velocity, then they will reach the plate at the same time. But as Guges said, even if you throw them at the same initial velocity and trajectory, inertia is going to effect them differently, causing them to have different rates of horizontal velocity throughout their flights. Friction of the material against the air, and other things would of course come into account, too...

The whole point of hop-up, creating a backspin on the BB, is that it effectively counteracts the force of gravity (albeit at the sacrifice of some horizontal velocity).
Gill wrote:Does that equate to the loss of fps when BB weight goes up? Elaborate please. :D
No. The spring in your gun, and the compression you get in the cylinder, exerts a certain amount of air pressure (and force), that can be applied to your BB. As F = ma, and the force is more or less a constant, a BB with a larger weight/mass will have less acceleration. That lower acceleration is what yields the lower FPS.
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Re: Example of Inertia - why you should use heavier bb's.

Post by Gill » Mon Jul 12, 2010 9:43 am

I understand now that there is a lot of physics that my high school graduate mind has yet to learn. :lol:

Thanks for clearing that up for me, I already use .25 all the time in my AEG so I have nothing to be worried about.

Very interesting topic by the way, especially for what I was always told about .25's lacking in range. I feel more confident using them now. :D
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Re: Example of Inertia - why you should use heavier bb's.

Post by Guges Mk3 » Mon Jul 12, 2010 10:10 am

For the pitcher with the steel ball how much of a weight increase are you talking about, 2x, 3x, 5x, 10 times? There is a point of diminishing returns due to this being a closed system.

This is also why people shoot lead out of guns instead of wood.
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Don't fear the gun...fear the one that's wielding it!

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