Impact formula

[Insaneride]

BTW, thanks JohnBartley.

[Willie B]

No, No, No, A gun is sighted for a stationary target. If hypothetically, the gun is sighted for 100 yards, the monkey is at 100 yards, only a stationary monkey dies.

If the monkey lets go of the branch he will fall to earth. Since the sighting of the rifle compensates for gravity, it will arrive after the monkey is gone.

If the monkey hunter's only quarry is falling monkeys, he will calculate the distance between barrel, and scope, sight his rifle parallel to the scope, and aim that far above the heart.

No hunter ever thought that way.

As we fire the rifle, we know gravity will have its way. To compensate, we point the scope lower than the line of bore. I sight for 200 yards. As I fire the bullet leaves the muzzle 1.75 inches below the line of the scope. If sighted for 200 yards, the bullet rises to meet the line of sight at 200 yards. Closer distances, bullet is slightly lower than sight.

At 200 yards the bullet rises a bit above line of sight, but gravity, air resistance, and earth curvature take over. It rises a bit above the line of sight, but not far.

At 100 yards my 7MM will still be rising. The monkey will be falling. Though my projectile is still rising, and hasn't yet attained its full height in its arc, (it is still below line of sight), the monkey has been falling throughout. A bullet aimed for a heart shot might graze his head hair. The monkey is gone.

He has now emigrated to Zanzibar while we idiots argue about aiming a gun.

[Tbones]

Math is hard....

[ronsii]

Apparently shooting monkeys is harder...

[Oscar]

I was trying to pound it into this woman's head the student was right, book, and teacher were wrong. Mrs. B was getting upset, so I dropped the subject, and let this sanctimonious B**** go on thinking she was right.

The teacher was introducing basic concepts of kinematics in the face of gravity, without going into, or even knowing, the specifics of rifles and real-life ballistic projectile trajectories. The only thing wrong was her "scenario", because she didn't know the specifics of firearms/scopes/etc, and that was HER mistake, Not physics. Not "the book". Not even the teacher's underlying idea was incorrect. If your son is so smart, then he would have realized what the teacher was doing was INTRODUCING the basic underlying idea has to do with basic projectile trajectories analyzed in their independent x- and y-components. To say that the "oh the book was wrong, my son/daughter knows more" and/or "oh the teacher's wrong, my son/daughter know more than they do" what is wrong with some parents. Yes there are some bad teachers out there (I've worked with some), but the books are hardly ever wrong. Somehow the PhD physicists got it all wrong after all the studying that they did and knowledge acquisition they have come to have? Right. I would be very hard pressed to think that actual "scenario" was presented in a respected, published high-school level physics book. What is the ISBN of this physics book so I can look it up and read that problem as it was stated? Going from your elaborate response, it sounds like you just wanted to tout out what you knew about firearms to try and make the physics teacher look bad/incompetent. It's not hard to read between the lines.

[MinnesotaDave]

The teacher was introducing basic concepts of kinematics in the face of gravity, without going into, or even knowing, the specifics of rifles and real-life ballistic projectile trajectories. The only thing wrong was her "scenario", because she didn't know the specifics of firearms/scopes/etc, and that was HER mistake, Not physics. Not "the book". Not even the teacher's underlying idea was incorrect. If your son is so smart, then he would have realized what the teacher was doing was INTRODUCING the basic underlying idea has to do with basic projectile trajectories analyzed in their independent x- and y-components. To say that the "oh the book was wrong, my son/daughter knows more" and/or "oh the teacher's wrong, my son/daughter know more than they do" what is wrong with some parents. Yes there are some bad teachers out there (I've worked with some), but the books are hardly ever wrong. Somehow the PhD physicists got it all wrong after all the studying that they did and knowledge acquisition they have come to have? Right. I would be very hard pressed to think that actual "scenario" was presented in a respected, published high-school level physics book. What is the ISBN of this physics book so I can look it up and read that problem as it was stated? Going from your elaborate response, it sounds like you just wanted to tout out what you knew about firearms to try and make the physics teacher look bad/incompetent. It's not hard to read between the lines.

I actually had the same question twice when I went to college.
I think you'll find that his textbook contains questions similar to below.

First time it was an arrow aimed directly at the monkey. In other words, no arc for proper shot placement.
In this slower scenario it's easier to visualize that gravity will affect both monkey and arrow over what ever time period it takes the arrow to get to the monkey.
Other possible variables are also neglected in this simplistic style question.

The second time it was a bullet. Also aimed directly with no arc for proper shot placement.
The time is much shorter, but to the same end.
Again, any other possible variables are neglected.

An additional question, preceding the other two, was the classic:
"Which bullet hits the ground first? One aimed parallel to the Earth, or one dropped at the same time as the other is fired."

Now, in my opinion, this question has to neglect the curvature of the Earth to assume a bullet could be fired "parallel."

The wording of the question is critical.

It's very common for students to "read into" a question based on personal tangible experience, instead of taking the beginning fundamental questions at face value.

This is where the teacher's pre-loading of the thought process is important. Students have to be made to understand that math/physics always starts with the fundamental style questions before adding in the complexity of additional variables.

If the teacher does not do this, students can easily misunderstand what is being asked.

[Oscar]

The wording of the question is critical.

It's very common for students to "read into" a question based on personal tangible experience, instead of taking the beginning fundamental questions at face value.

This is where the teacher's pre-loading of the thought process is important. Students have to be made to understand that math/physics always starts with the fundamental style questions before adding in the complexity of additional variables.

If the teacher does not do this, students can easily misunderstand what is being asked.

Us being educators, we can see the nitty-gritty details of a lot of these types of questions, and know that the wording is very, very critical, because we know that what we're teaching is just the basics for students to barely grab onto a complicated subject. The teaching is also focused on how to learn, so that when they go into advanced studies, that's where they can learn the real details of a complicated system as much on their own as possible. Willie and his son don't understand all this, as evidenced by his reply about the situation with his son's physics teacher as he described it. A lot of people are un-aware of what goes into writing state-mandated curriculum standards, which teachers have to abide by, as well, as per their actual teacher job descriptions/contracts. In very few physics courses would you every encounter truly specialized scenarios, and I would know as I took and aced AP Physics 1 & 2 when I was in high school. Heck there is hardly any calculus in AP physics! In the real world, you can't even begin to think about calculating/predicting anything with any kind of certainty if you don't know multi-variable calculus and partial differential equations with a nice healthy dose of linear algebra to work out some nifty matrices.

Willie, your son's physics teacher had to learn quite a bit (even if it doesn't seem like it) to teach high school physics, such as this: Diagonalizing the Inertia Tensor. And that's just the basics from a Classical Mechanics course. Give them a break, would ya.

[Willie B]

I know this teacher was unwilling to entertain the concept that bullets don't fall short range because sights compensate. She was upset that a student understood where she did not. Someone had to pay. Despite having time to research, she still considered his claim that bores are not parallel to sights to be "ridiculous" She carried her presumption to the parent conference still willing to fight it out. She was wrong, and unwilling to admit it.

What amazes me is that hundreds of students before Zack never challenged her.

I can prove that 10 bullets fired from a rifle at 100 yards can hit near bullseye showing little evidence of the effects of gravity. A monkey will fall, few will argue.

[Insaneride]

Whatever caliber it is that is traveling 2000 fps will take about 1/4 of a second to get there but more than likely drop 10 to 12 inches. You would have to describe the exact cartridge to verify that.

Oh, BTW we do have calculations for gravity distance vs ground distance that we will continue to use in spite of your misinformation. It's often referred to as the true Ballistic Distance. Some sporting range finders even have that function built in.

Nothing falls at 32 feet per second untill the point of that 1st second has been reached and so-on. Everything in a free fall test starts a zero and builds up to the 32 ft per second per second. Remember it's called rate of acceleration. Like zero TO 60 in X seconds not 60mph for X seconds. Big diff. And yes you've done enough here.

You are correct that the bullet will only fall 12" in 0.250 seconds. Some books say 1/2 times 32'/sec^2. My math was off times two. The Hornaday ballistic charts helped me find my error. All my math was double the charts and that's when I rembered why 16' should be used instead of 32'. Even metric formulas show 9.8m/sec^2. Hope that helps.

[Sandy]

I Think we're all good here. Nothin wrong with a little cussin back and forth once in a while. Keeps the mind sharp. I have a unique talent of not hanging on to little day to day scraps. Next day it's all gone and I'm off chasing butterflies. Next time the same subject comes up I'll argue the other direction just for chits and giggles.

[Oscar]

I can prove that 10 bullets fired from a rifle at 100 yards can hit near bullseye showing little evidence of the effects of gravity. A monkey will fall, few will argue.

What you can't prove/demonstrate is how a spinning ballistic projectile does not have the same force(s) exerted upon it as an object simply released from a height. A spinning ballistic projectile can have angular momentum/force vectors imparted to it that can change the course of it's trajectory, because energy from the gunpowder explosion ultimately is transformed into rotational kinetic energy as the bullet travels/leaves the bore, and it is this kinetic energy which can impart forces that can counter-act the effects of gravity. Basic examples of this may be found in a Classical Mechanics physics textbook. I know someone said "everything falls at 32 ft/sec²", which is semi-true, but that is only for objects released from a height and not too subject to aerodynamic drag or any other external forces, and not necessarily true for objects that are subject to external forces as analyzed by the appropriate force vector diagrams.

[Willie B]

What you can't prove/demonstrate is how a spinning ballistic projectile does not have the same force(s) exerted upon it as an object simply released from a height. A spinning ballistic projectile can have angular momentum/force vectors imparted to it that can change the course of it's trajectory, because energy from the gunpowder explosion ultimately is transformed into rotational kinetic energy as the bullet travels/leaves the bore, and it is this kinetic energy which can impart forces that can counter-act the effects of gravity. Basic examples of this may be found in a Classical Mechanics physics textbook. I know someone said "everything falls at 32 ft/sec²", which is semi-true, but that is only for objects released from a height and not too subject to aerodynamic drag or any other external forces, and not necessarily true for objects that are subject to external forces as analyzed by the appropriate force vector diagrams.

We are now VERY far afield. As OP I reserve the right to go far afield. Lets depart from high school curriculum, and explore. I'll be the student.

It has long been my opinion that teachers sometimes work from simplistic textbooks while they don't understand the subject. When they encounter a student thinking beyond textbook, or teacher, the teacher is threatened. Their inappropriate reaction changes the relationship with the student, not for the better. It often interferes with learning.

[Insaneride]

What you can't prove/demonstrate is how a spinning ballistic projectile does not have the same force(s) exerted upon it as an object simply released from a height. A spinning ballistic projectile can have angular momentum/force vectors imparted to it that can change the course of it's trajectory, because energy from the gunpowder explosion ultimately is transformed into rotational kinetic energy as the bullet travels/leaves the bore, and it is this kinetic energy which can impart forces that can counter-act the effects of gravity. Basic examples of this may be found in a Classical Mechanics physics textbook. I know someone said "everything falls at 32 ft/sec²", which is semi-true, but that is only for objects released from a height and not too subject to aerodynamic drag or any other external forces, and not necessarily true for objects that are subject to external forces as analyzed by the appropriate force vector diagrams.

Where you are confused is: the horizontal vector is from the gyroscopic effect. Secondly and also, the gravitational Force is 16'/second^2. Gyroscopic and and or bullet mass don't escape gravity.

Edit: gyroscopic changes azimuth or horizontal. No?

Gyroscopic effects Azimuth, not elevation.

[John Bartley]

Edit: gyroscopic changes azimuth or horizontal. No?

Gyroscopic effects Azimuth, not elevation.

Neither. Spinning the bullet stabilises it in it's position in the air .... ie : keeps it from tumbling, wobbling etc. Doing that allows the bullet to travel farther due to decreased air resistance (keeps the pointy end forward). A steady wind from starboard will still push the bullet to the left and gravity will still cause it to sink all at the same time as the gyro effect keeps the pointy end to the front.

These are pretty pared down and basic answers to questions about concepts which are much more complex than I know how to answer.

My impression of the "teacher vs student" conflict is that the teacher was ignoring the art of rifle shooting while pursuing teaching about gravity and thus forgot that the rifle sights already compensated for some gravity in the initial sighting. When confronted with a student who knew about sights and leading moving targets, the teacher got flustered and refused to admit that the lesson plan did not account for rifle sighting and was simply teaching about gravity and not how to shoot. There could have been some middle ground reached there had the teacher explained that.

my $0.05 (no pennies up here)

[MinnesotaDave]

We are now VERY far afield. As OP I reserve the right to go far afield. Lets depart from high school curriculum, and explore. I'll be the student.

It has long been my opinion that teachers sometimes work from simplistic textbooks while they don't understand the subject. When they encounter a student thinking beyond textbook, or teacher, the teacher is threatened. Their inappropriate reaction changes the relationship with the student, not for the better. It often interferes with learning.

For myself, I respectfully disagree.

The simplistic textbooks I teach from are for the benefit of introducing topics to students, not because I don't understand the higher level material.

My math degree goes WAY beyond the math I teach in high school

I encourage students to think beyond the textbooks as often as possible.
There are sometimes students who learn at a faster pace, and earlier in their life, than I ever would have been able to as a teenager.
They are the most fun to teach and are in no way threatening.

[Willie B]

I did not say it was true of all teachers. In fact, (I believe), it is true of only a small segment of teachers.

Teaching is like a chain, no stronger than its weakest link. Only a devoted few have no weak link. Also, the student can provide the weak link. Too often learning, (preparation for adult life), fails. I wish fewer students would fall through the cracks.

I believe you Dave would walk through Hell on Sunday to make a difference in a student's life. We need more like you.

[MinnesotaDave]

I did not say it was true of all teachers. In fact, (I believe), it is true of only a small segment of teachers.

Teaching is like a chain, no stronger than its weakest link. Only a devoted few have no weak link. Also, the student can provide the weak link. Too often learning, (preparation for adult life), fails. I wish fewer students would fall through the cracks.

I believe you Dave would walk through Hell on Sunday to make a difference in a student's life. We need more like you.

I am humbled to receive such high praise - thank you

[Insaneride]

John Bartley, I believe you know ballistics and the gyro effect goes way beyond Willies monkey. It has been a good topic but we don't know how the teacher worded the problem/excercise and I think it would be better understood if a spear was used or a laser sight but that's my opinion. I believe Willies son could have shot the monkey and that the teacher was just trying to teach and this has gave us all something to think about.

As to the gyro effect; there is a force caused by the spinning called precession. I looked up ballistic effects and found this video. At around the 10:00 mark, it shows how the effect causes an azimuth shift at long range. They also mention at very long range, the Earth spinning causes a shift. I'm not trying to contradict because we saw where that got me but this is a good video.



ronsii, here's a video for you explaining the gyro effect. Your rite that it isn't noticeable with a grinder but I've noticed a lightness using a screw gun tho. Check it out.

[William McCormick]

Correct. No argument about the science or the results. The reason .... is because the gyroscopic effect of a spinning bullet is to resist forces that cause the bullet to change how it is positioned in the airstream (stability - reduced wobble) . It stays pointed ahead and being pointed ahead (pointy end forward) has less air resistance, resulting in slower speed decay due to friction, so it travels farther. The effect of gravity remains constant, so while the bullet travels forward it descends. The distance may be longer, but the time will be the same before it hits the ground. The difference between a round travelling fast and one travelling slow is that when the slow round (think muzzle loader round ball) hits the ground it isn't going to ricochet very far compared to say ... 22-250 which will ricochet and travel another huge distance before falling to ground again.

If you take a look at two projectiles passing the earth at the same distance from the earth. One going very fast the other slow, one will get pulled into the earth and burn the other will pass by the earth with little couse change. I am sure that there will be a difference in how gravity effects objects based on their velocity as well as any gyro effects.

[John Bartley]

If you take a look at two projectiles passing the earth at the same distance from the earth. One going very fast the other slow, one will get pulled into the earth and burn the other will pass by the earth with little couse change. I am sure that there will be a difference in how gravity effects objects based on their velocity as well as any gyro effects.

Yes, again you are correct in how the objects will move. The things to remember are that 1) gravity is a constant that diminishes with distance from the object exhibiting the gravitational pull and 2) earth is curved while the trajectory of the objects is (assuming no other forces exerted on them) is straight. As long as both those objects are at the same altitude above earth they will be affected the same way. The difference between them is speed, and one (the fast one) will travel farther before it drops enough to be trapped by the gravitational pull of earth (earth is curved). If it is travelling fast enough it will travel thru' the gravitational field and exit it before losing enough altitude to be trapped.

[William McCormick]

I actually had the same question twice when I went to college.
I think you'll find that his textbook contains questions similar to below.

First time it was an arrow aimed directly at the monkey. In other words, no arc for proper shot placement.
In this slower scenario it's easier to visualize that gravity will affect both monkey and arrow over what ever time period it takes the arrow to get to the monkey.
Other possible variables are also neglected in this simplistic style question.

The second time it was a bullet. Also aimed directly with no arc for proper shot placement.
The time is much shorter, but to the same end.
Again, any other possible variables are neglected.

An additional question, preceding the other two, was the classic:
"Which bullet hits the ground first? One aimed parallel to the Earth, or one dropped at the same time as the other is fired."

Now, in my opinion, this question has to neglect the curvature of the Earth to assume a bullet could be fired "parallel."

The wording of the question is critical.

It's very common for students to "read into" a question based on personal tangible experience, instead of taking the beginning fundamental questions at face value.

This is where the teacher's pre-loading of the thought process is important. Students have to be made to understand that math/physics always starts with the fundamental style questions before adding in the complexity of additional variables.

If the teacher does not do this, students can easily misunderstand what is being asked.

There is no parallel path, to the earth's surface, only thing close is a stable orbit, that is part of the problem. However, at some velocity, the bullet will go into a stable orbit, if you positively accelerate it further, it will raise from the earth's surface, making all the calculations seem rather silly.
At sea level, I believe the velocity is 32,000 feet per second approximately, to void the effect of gravity. We used to do these calculations in the fourth grade, so forgive my memory. My point is whatever the force of gravity on let us say a 1,200 feet per second round is, it will drop 1,200/32,000 less than a bullet dropped and allowed to fall straight to the ground. So I am pretty sure all the "precise" calculation have errors.

Sincerely,

William McCormick

[Insaneride]

The Earth's escape velocity is 25,030 miles per hour or 3,700 feet per second. Ironically, the Earth has a circumference of approximately 25,000 miles or the escape velocity in mph. This irony Probly doesn't apply using the metric system tho.

[William McCormick]

If the escape velocity is 25,030 miles per hour, the calculation would be 25,030 miles times 5280 feet which comes to 132,158,400 feet per hour. Divide that by sixty and you get 2,202,640 feet per minute. Divide that by sixty and you get 36,711 feet per second. So the exact formula for a bullet at 1200 feet per second would be 1200/36,711 it will drop 0.03268775026558797 less than a bullet just dropped stright to the earth. It matters greatly whether you fire the round from East to West or West to east. North and South will remain the same.

Sincerely,

William McCormick

[William McCormick]

Even sea level can be off by thirty feet, depends on where and when you do the test.

Sincerely,

William McCormick

[William McCormick]

Where is Dave when you need him?

Sincerely,

Wiliam McCormick