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Where do you aim at the target if it falls when you pull the trigger?

  • Above the target.

    Votes: 0 0.0%
  • At the target.

    Votes: 17 73.9%
  • Below the target.

    Votes: 3 13.0%
  • You can't know; It depends on velocity.

    Votes: 3 13.0%
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Discussion Starter #1 (Edited)
I am taking Mechanical Engineering Technology and will be finished this spring. One question that was asked is ballistics related - how many of you can get it right?

Keep in mind that this is more of a theoretical question, not a real-world question. Things like wind, air resistance, and time from trigger pull to bullet exiting the barrel is neglected.

You are going to shoot at a target that will fall as soon as you pull the trigger. Where do you aim? Above the target, below the target, at the target, or it depends on velocity?

Please don't explain you answer until the poll is done in one week (let others put in their vote first), then we can talk about it.
 

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Are we assuming the sights are aligned to be parallel with the barrel, and not designed to raise the barrel slightly for a trajectory? That's how this type of question is usually put.
 

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Discussion Starter #5
Are we assuming the sights are aligned to be parallel with the barrel, and not designed to raise the barrel slightly for a trajectory? That's how this type of question is usually put.
Sorry, I thought about this later. This isn't where the scope is aimed, but rather where the bore is aimed (if you were to pull the bolt out and look down the barrel).

And may we assume that the target was placed at the same height as the barrel before it started to fall?
That can be part of the discussion on Sunday. Make The assumption if it helps you pick an answer.


I'm not trying to toot my own horn here - I've taken a total of 2.5 years of engineering classes and I still got the question wrong. :rolleyes: This isn't so much a competition but an exercise in physics.

Later we'll talk about the feasibility of perpetual motion. :p (jk)
 

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If the bore is aimed at the target, then I know the answer. However, I'll wait and see what gets posted before I say anything. I had a quite similar issue come up in my physics class many moons ago in college. The professor actually had a device that demonstrated the answer. Interesting question. :)
 

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Discussion Starter #7
If the bore is aimed at the target, then I know the answer. However, I'll wait and see what gets posted before I say anything. I had a quite similar issue come up in my physics class many moons ago in college. The professor actually had a device that demonstrated the answer. Interesting question. :)
So did mine. We played with it for half an hour - lots of fun!

Thanks for waiting to say the answer, I appreciate it! :)
 

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I was a physics major. Sometimes I wonder why things aren't as obvious to others, but I expect most will get this right.
 

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Assuming the target is 100yards away, Assuming the average projectile is moving 3000 ft/sec. the difference in time is .1 sec for the projectile to leave the end of the barrel and reach the target. At the time the bullet strikes the target. Accelleration due to gravity is 9.8m/sec/sec or 9.8m/sec2(squared)
At the end of the .1 sec the target would be falling at 9.8m/100 or .098m/sec but due to constant acceleration from 0m/sec the target would have only fallen 1/2 of the velocity of which it is traveling at that moment in time. 1m=39.67" so 9.8m/100 is 3.89"/2(due to accelleration from 0) means the target would have only fallen 1.94" So if you are using a scoped rifle zeroed at 100yards or an iron sighted rifle your point of aim should be 2" below, however if the rifle is bore sighted to the target all things fall at the same speed (neglecting wind resistance) and you should just aim at the target. I'm guessing that if the the professor is neglecting wind resistance, Ballistic coefficient, distance from target, velocity of projectile, humidity, temperature, elevation above sea level, elevation difference between rifle and target. Due to the extreme lack of vital information in the proposed question. I am goinng to go with the most simplistic answer.

FLAME ON
 

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Gravity causes them both to fall at the same rate.
 

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Assuming the target is 100yards away, Assuming the average projectile is moving 3000 ft/sec. the difference in time is .1 sec for the projectile to leave the end of the barrel and reach the target. At the time the bullet strikes the target. Accelleration due to gravity is 9.8m/sec/sec or 9.8m/sec2(squared)
At the end of the .1 sec the target would be falling at 9.8m/100 or .098m/sec but due to constant acceleration from 0m/sec the target would have only fallen 1/2 of the velocity of which it is traveling at that moment in time. 1m=39.67" so 9.8m/100 is 3.89"/2(due to accelleration from 0) means the target would have only fallen 1.94" So if you are using a scoped rifle zeroed at 100yards or an iron sighted rifle your point of aim should be 2" below, however if the rifle is bore sighted to the target all things fall at the same speed (neglecting wind resistance) and you should just aim at the target. I'm guessing that if the the professor is neglecting wind resistance, Ballistic coefficient, distance from target, velocity of projectile, humidity, temperature, elevation above sea level, elevation difference between rifle and target. Due to the extreme lack of vital information in the proposed question. I am goinng to go with the most simplistic answer.

FLAME ON
I think you missing a couple obvious things like the moon's affect on gravity and the troubling affect of solar flares. Don't even get me started on how global warming affects all this!!!







:D
 

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Assuming the target is 100yards away, Assuming the average projectile is moving 3000 ft/sec. the difference in time is .1 sec for the projectile to leave the end of the barrel and reach the target. At the time the bullet strikes the target. Accelleration due to gravity is 9.8m/sec/sec or 9.8m/sec2(squared)
At the end of the .1 sec the target would be falling at 9.8m/100 or .098m/sec but due to constant acceleration from 0m/sec the target would have only fallen 1/2 of the velocity of which it is traveling at that moment in time. 1m=39.67" so 9.8m/100 is 3.89"/2(due to accelleration from 0) means the target would have only fallen 1.94" So if you are using a scoped rifle zeroed at 100yards or an iron sighted rifle your point of aim should be 2" below, however if the rifle is bore sighted to the target all things fall at the same speed (neglecting wind resistance) and you should just aim at the target. I'm guessing that if the the professor is neglecting wind resistance, Ballistic coefficient, distance from target, velocity of projectile, humidity, temperature, elevation above sea level, elevation difference between rifle and target. Due to the extreme lack of vital information in the proposed question. I am goinng to go with the most simplistic answer.

FLAME ON
WAAAAY over thought.

Gravity causes them both to fall at the same rate.
Spoiler!
 

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Theanswer is at the target. gravity pulls them down at the same rate, as MikeG has allready stated
 

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If the rifle is zeroed at the same range, shooting AT the target, where drop has already be adjusted for, will put the bullet exactly where the target was when the fall started.

With any moving target we must aim at where it's going to be when the bullet arrives at the same point in space.
 

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What if we dimple the spinning bullet like a golf ball?
 

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Discussion Starter #18
Well thanks for everyone for voting, it seems the majority of you was right. Since both fall at the same rate, if you aim the bore at the target, you will hit the target.

I answered "it depends on velocity" in school, and subsequently got flamed for choosing wrong (guess I should have known :oops: ).

Thanks again for playing. :)
 

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The simultaneous drop thing usually only works in a vacuum. In air, the correct answer for most bullet shapes is you will have to bore sight slightly below the target, but not nearly as far below as the target is going to fall during the bullet time of flight. That is because most bullet shapes pitch slightly upward in flight, creating a small lift component. Thus, they do not fall quite as fast as they would if simply dropped from a stationary position.

An example of an exception would be a round ball projectile, though it must be spin stabilized to prevent any rotation on a horizontal axis not coincident with the trajectory. If it gets that, it will either have lift or act like a sinker ball, depending on which way the rotation is going? Not to mention veering off to the side.

Of course, this can all work out backward if the target is paper and is far enough away? If you are at, say, 1000 yards, and the bullet is going to take well over a second to arrive, then air pressure may have time catch the bottom edge of a paper target sliding down the backer and start it turning onto its back, in which case it may be the slower falling object of the two? But this won't be a consistent problem. Bullet lift will.
 

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"You are going to shoot at a target that will fall as soon as you pull the trigger. Where do you aim? Above the target, below the target, at the target, or it depends on velocity?"

"it seems the majority of you was right. Since both fall at the same rate, if you aim the bore at the target, you will hit the target."


Your intitial premise didn't specify that you/we were aiming "the bore" at the target. That, vs. the line of sight on a zeroed rifle which is corrected for drop over the 'as fired distance' do make a difference, don't it?
 
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