Dodge a Bullet

[tlouis1324]

Dodge a Bullet

Adam and Jamie called in a U.S. Army sniper for some preliminary tests to measure the time it took for a bullet to reach its target. After some failed attempts, they obtained travel times of 231, 597, and 1791 ms for distances of 200, 500, and 1,200 yd (180, 460, and 1,100 m), respectively. Next, the pair did some workshop tests to find how quickly they could dodge a shot, using a camera flash to simulate the muzzle flash. Jamie proved slightly faster, dodging in 490 ms; based on this result, he and Adam calculated that the shooter would have to be at least 400 yd (366 m) away.
They then watched Dave fire standard blank cartridges from various distances and found that they could not see his muzzle flash at all past 200 yd (183 m). When he switched to Hollywood-style blanks with much heavier gunpowder loads, they could easily see the flash out to 1,200 yd (1,097 m). Finally, they set up a blank-firing rifle at 200 yards, wired to a timer and paintball gun; when one man pulled the trigger, a paintball would be fired directly at the other’s chest after 231 ms. Neither was able to dodge any shots until the rifle was moved to 500 yd (457 m) (600 ms delay) and loaded with Hollywood blanks. Adam and Jamie declared the myth busted, since an actual sniper would take precautions to ensure that the target would not see the muzzle flash.

I need to know the control, independent variables, dependent variables and constant variable for the experiment.

[deleted-249560]

Let's see if we can figure that out.

They tried several experiments using the same cartridges and various distances.

a) What stayed the same between tests? These are your constants or constant variables.

b) Between any two trials, what *one* thing did they change? That would be your independent variable.

c) As a result of that change in b), what measurement changed? That would be your dependent variable.

Look over your description and I think you'll answer your own question.

Howard

[tlouis1324]

There were so many changes because they tried with standard blank cartridges, Hollywood style blank cartridges and then then paint ball gun. This is what I came up with.

Independent Variable: Distance
Dependent Variable: Reaction time, cartridges
Constant Variable: cartridges????
Control: Gun firing at the same speed

[bradleyshanrock-solberg]

Hm...some problems.

The first two (blanks and hollywood blanks) they are measuring ability to dodge based on seeing the muzzle flash.

You don't actually need to do an experiment, the minimum distance can be calculated by knowing human reaction time and the difference between speed of light and speed of the bullet (most bullets travel a bit faster than the speed of sound - but it's close enough to give the idea....the problem is very like reacting to a lightning flash before the thunder is heard)

You'd also have to know how fast the human could go from a stopped position to move sufficiently far to cause a miss. Both reaction time and speed would vary between people but not very much compared to the "flash-boom" interval. I expect you could get a pretty solid guess for minimum distance just from that - and if the flash of gunfire wasn't visible at that distance then yes, you have debunked the idea right away.

The paintball gun is another animal. Paintballs travel MUCH slower than bullets (this is a lot of why they only sting and bruise when they hit, instead of causing horrible wounds). So dodging a paintball is a much easier proposition in terms of reaction time...however there is no muzzle flash with a paintball round.

What they did to get around this issue is to pick a different distance for the paintball gun, one that simulated the time gap for the more distant rifle. That's a fairly clever solution although without doing the math I can't guess how well they got the distances right.

So....they didn't measure for different humans, they stuck to "can this one human dodge a bullet" as their question (another experiment might have somebody nearsighted or out of shape compared to a stunt man, say). They controlled for the ability to dodge by having the paintball gun which was much closer to the target round simulate a rifle bullet (I will assume they did the math correctly on relative speed of bullet vs paintball round). Their variable was distance - moving the rifle further away until the paintball could be dodged, and their conclusion was that the rifle would have to be quite far from the target. I'm not sure the myth is busted - snipers often have tricks to conceal m muzzle flash but your average shooter with a rifle does not - and the range listed is right around the typical effective range for a 50/50 hit ( http://gunwiki.net/Gunwiki/FactorsOfEffectiveRange). At that range it seems like a person who notices the muzzle flash could move quite a bit and degrade the 50/50 hit odds to something much lower (no choice is perfectly safe as you can always move by accident into the bullet path of a miss...where freezing up would have been better than moving).

Very interesting experiment, reasonably well set up, but I'm not sure the conclusions are sound. I'd say the conclusions are only sound if you can't see the rifle flash without special precautions to conceal it (eg, at night it might be easier to dodge a bullet than if the sniper is shooting you from the east, at dawn when you are looking into the sun)

[tlouis1324]

Thanks for responding. I am still at a lost and need the answers to these as soon as possible for the experiment. Are these correct or incorrect? Help

Independent Variable: Distance
Dependent Variable: Reaction time, cartridges
Constant Variable: cartridges????
Control: Gun firing at the same speed

[deleted-249560]

You're on the right track but i think you're confusing this whole series of tests as *one* experiment when it's several.

If the marksman used the same gun and the same type of cartridges but the observer moved closer or farther away, then the distance is indeed the independent variable, the reaction time is the dependent variable as you stated and the constants would be the gun and the cartridges. If a bullet were involved, keeping the cartridge the same is critical as different bullets will travel at different speeds from the same gun.

They then changed the cartridge to one that created an extreme muzzle flash. The point of that was to make something visual to see whether you could detect the gun firing faster if you used your eyes instead of your ears. If they stood at the same test distances as before but then reacted based on the light, the distances were now constants and the independent variable was the cartridge.

You were absolutely correct when you identified there were so many changes. There were. When you realize it was actually a series of experiments where one was designed to work with the date fro the one before, it's a lot easier to break it down. Any one successful experiment only has a single independent variables. Everything else has to be the same, otherwise you can't tell what made the difference.

With humans involved Adam and Jamie also didn't take into account that we get better at a task with practice, so in theory they could have gotten better at reacting to the sound or flash as the experiment moved forward. They also could have gotten tired, so they could have gotten worse. That wasn't factored in at all - it's hard to do that, but important. I think you can discount that but consider it in your own experiment.

Are you designing your own experiment based on the show?

Howard

[bradleyshanrock-solberg]

To break it down further.

0. You can't dodge a bullet based on the sound. Bullets normally travel faster than sound (the "crack" of a bullet is a sonic boom), so the bullet will hit a person before the sound arrived.

1. They had to do an experiment to know how fast a rifle bullet is, and another to know how fast a painball round is. (without this, they can't set the distance of their paintball gun relative to the rifle to get a realistic measurement). (this part of their procedure is pretty sound, assuming they took enough shots to gain confidence in their numbers)

2. They used a camera flash to simulate a gun, and measured how fast the test "human" could move to estimate if he could force a miss from an accurately aimed round, and came up with a rough figure of 400 yards (issue - different humans move at different speeds, have slightly different reaction times, might be affected by fatigue etc. However their estimate is very rough, and the differences in human ability to dodge probably isn't large compared to the "about 400 yards" outcome..that result is "accurate" from 350 to 450 yards, which should be well within human variation...if they said "about 410 yards" it'd only be "accurate" between 405 to 415 yards and human variation might matter there. By "accurate" I mean "accurate with a precision of one significant digit".https://en.wikipedia.org/wiki/Significant_figures )

3. They then used a real rifle instead of a camera, and the human couldn't see the flash at that range. (issue - this is highly dependent on both light conditions and training and also familiarity with the environment. Humans notice change in patterns very well if they're trained to think a certain change is important. I don't have to be paying attention to notice a dog darting into the road when driving because I've decades of driving experience. When I was 16, just learning, I'd have to be actively watching. I would guess a soldier who has done time in a war zone similar to where the test was run might do a lot better, as would holding the test at night or if the shooter is firing out of shadows rather than somewhere brightly lit).

4. They increased the charge in the rifle to make it more visible (this is a somewhat odd response compared to, say, changing the lighting conditions), but it let them try the next bit, where they discovered that dodging bullets is harder than they estimated in step 2, and moved their range out to 500 yd.

Because they figured nobody could see a rifle flash at 500 yd, they concluded the myth was busted. I would be very interested to see if a veteran would agree with them. 500yd is pretty far out for a rifle shot, there's a good chance it would miss anyway with average quality rifles and marksmanship, but moving suddenly in response to the muzzle flash, if you noticed it, would probably hamper the odds of a hit quite a bit.