at 1.42 yes that's true, in a vaccum! Air resistance affects things differently eg feather, vs leadshot, and with the horizontal speed thing, the bullet will in reality fly longer, because of the rifle's zero the bullet has a slight upward trajectory, therefore parabolic calculations need to be applied
australiansurvival Right. Technically, it is a parabolic calculation. Starting horizontally, the projectile`s trajectory follows a curve, half a parabola (from apex down). I`ll make another calculation "projectile launched at an angle", thanks for the idea & watching.
My former boss had us storing 7 lb. objects 6 feet off the ground. After getting the formula from an ME friend, I calculated that it would really, really hurt if the object fell on my foot.
+theoverengineer I was always hoping my boss might become involved in such a test since not only would the part be falling fairly fast but would hit a .25x.25 inch spot one one's foot.
You should state that you are assuming constant velocity (arrow doesn't have wind drag). This is a fair assumption for 30 meters but not for 60 meters.
Yes, good point, thanks. I also assume uniform acceleration (hardly ever the case) through the limbs` range of motion, and uniform tension in the string, so I calculated with average acceleration and force by measuring it at every 5cm (2in). Fish scale is hardly scientific, it is by no means a calibrated load cell, but my focus here is not to qualify people in artillery calculations but to improve shooting accuracy by providing a simplistic way to predict ballistic trajectory somewhat reasonably
Gravity is a good starting place for sure but the dynamics of a projectile through the fluid or medium known as atmosphere is vastly more complex. An arrow seems to use the underside of the shaft surface area to generate lift or at least resist downward motion. The AOA (angle of attack) relative to a horizontal reference is gradually changing. The arrow being an airfoil would have a boundary layer, drag coefficient, laminar flow, and other factors such as Bernoulli's Principle to consider it's trajectory as it transits through velocity decay. By placing an arrow in a wind tunnel (I'm sure someone must have tried it) the drag, upward lift along the underside of the shaft, pressure differentials and a host of data that are beyond my ability to gather would make an interesting test. It would seem that gravity would have pulled the arrow to earth much sooner unless there was some lifting force acting along it's axis to resist a downward motion.
+Flickchaser Totally. Anyone finds wind tunnel testing of projectiles/arrow, please share a link. Complex life aside, here is an archer who can hit an aspirin (without math): ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Q8Yp9SjCU5E.html
+theoverengineer your link-@google "" (Aerodynamic Properties of An Archery Arrow-Research Gate)"" at web site www.researchgate.net You probably function at a higher level of math than I. The article contains some wind tunnel photos as well, but the math shown is beyond me at this time. Found the clip of guy shooting aspirin-thanks much. As a kid in the 50's we would sit in a darkened theater and watch film clips of Howard Hill. Some of the clips are here on YT if you are interested although low resolution quality.Howard Hill was considered by many to be the greatest ever to pick up a bow and arrow.(Wikipedia) His trick shooting and hunting dangerous game with only a bow are a matter of record.
my ar is for home defense only......i adjust my sight parallel to the barrel so my aim will be the same at any distance......im only concerned about the distance where the bullet can travel straight...when it starts to drop, thats too much to worry for a home defense situation
This is a grade 10 exercise. He did without air resistant, shape of the bullet and drag coefficient. The error is 10% for arrow and 1000% for 900m/s bullet.
The may strike the earth at the same speed from the same height at the same point on earth, but the do not fall at the same speed. They accelerate as they fall.
Nope. Speed has no direction. Speed can remain constant while an object accelerates. Take communications satellites for example. They remain in a fixed orbit by keeping their speed constant. They constantly accelerate because their direction constantly changes as they orbit. Acceleration is a change in velocity, not speed. Velocity has both speed and direction.
Don´t get me wrong, I don´t want to discredit your effort, but honestly: this might be good for small initial speeds and distances but if you´ re shooting for example an air rifle at 80 metres, this goes completely out of the window. The initial (muzzle) velocity is about 880 fps but after about 55 metres, the air resistance has slowed the bullet down to the point where it begins a more or less much steeper descent (depending on the ballistic coefficient of the pellet). Is it really necessary to calculate ballistics for 30 metres? Isn´t it better to put up targets every 5 - 10 metres up to 100 metres and make a small drop scale for your weapon you can take with you anywhere, estimate the distance, just read from the schedule, adjust your scope and hit your target? No calculations needed at all and I dare to say, the result will be much, much more precise.
theoverengineer I have already done that with my scope and it works great, very precise (but I must have seperate schedules for every type of ammo I use for being really "on the spot") - but take the 7 minutes to watch this video (link at the bottom) - I was amazed by this guy and his shooting "abilities" (it´s less ability than a very good gun and well marked scope) but there you can see, how razor-precise such a schedule can be if somebody knows how to use it properly (and for making it you don´t even need these computer made calculations/simulations of the ballistic curve if you put your shots on cardboard) - /watch?v=SvvOyKFMzy4
theoverengineer I have now found out that the software he uses is no professional software at all - it´s designed for airguns and it is Hawke ChairGun Pro and completely free of charge - google for it. I already downloaded it and i am impressed. It´s really ingenius. I think I´m gonna play a bit more with my airguns now.
You can look up "ballistics calculation" or "ballistics trajectory calculation" on google, you´ll find a lot to that topic. But with that distance, you´ll really have to take into account wind, temperature, air density and all that stuff to get an accurate result. Depending on the weather circumstances you would be well up to 500 m off target if you just calculated the basic trajectory. Maybe you could post your calculations, somebody might find the mistake.
You say "All things fall to the ground at the same rate regardless of their masses". Is that 100% true? I always thought materials fell at different speeds according to their density. In other words, the calculations you would use for a projectile made of lead must be different then the calculations for a projectile of another material. Is that correct, because your quote about falling speeds instantly confused me because it contradicted with I always believed about "rate of fall or drop" (for lack of a better term). Not trying to be smartass by the way....
bobcaygeonfrench Excellent observation, no problems with science questions. Yes the rate of drop is the same for a bearing ball or cube (of the same size) for Mercury, Zinc, Chromium or Tin. Especially when friction with air is eliminated (vacuum) gravity pulls everything with the same force, falling at the same rate. Brainiac - Do heavy objects fall faster than light objects ? Aristotle vs Galileo APOLLO 15 Hammer and Feather
NO, g is a constant. It was proven long ago by Galileo and demonstrated during a moon landing using a hammer and a falcon feather. Drag in the atmosphere was not addressed in the basic calculations demonstrated here. The bolt will slow the longer it is in flight through the air, this is addressed using BC or ballistic coefficient. For a short range and slow arrow it does not make much of difference but when shooting bullets at long ranges it make an enormous difference.
Something isn't making sense to me. If I go to one of the many free places online to compute my ballistics I can put in identical information but only changing the BC (ballistic coefficient) and my bullet drop for 2 different bullets traveling the same speed and the same weight, same size etc will have 2 different drop results for a given distance. Therefore you're not calculating in the resistance to air (BC) in your equation UNLESS you're saying both propelled items have the exact same BC. ps, I did like your math though, thanks
I have a question . Is there a formula to figure out a projectile (lead pellet ) fps out of the barrel . A spring loaded piston air rifle that forces air trapped behind the pellet out of the barrel . In front of the spring is a piston that has a seal and it forces all the air thats in the cylinder out and into the barrel . Here is what I know from 4 different pellet weights . I know that with a 11.9 gr pellet the fps is 987 . With a 14.5 gr its 958 and with a 15.43 gr its 946.5 and a 16.36 gr its 899.5 . Knowing this info ,how do I figure out the fps if I used a 18 gr pellet or a 30 gr pellet ?
Plot the numbers on a chart to make a graph to estimate 18 gr or 30 gr projectile`s initial speed. Fairly easy to do for field estimates, no heavy calculations or critical measurements.
How do you go about doing that ? Can you give me a example ? The only info I want is the FPS out of the barrel . The FPS numbers are from out of the barrel . I know I can use a crony to get the fps from any given pellet or I can do a drop chart from different distances . I just thought there might be some kind of math I could do if I had 5 different pellet weights and I know the FPS that goes with that weight .
+Samir Bavkar Good one. People at the bottom always lost battle (Battle of Crécy, Battle of Halidon Hill), also tanks, artillery, same stuff. Given equal firepower weapons the high position can outrange the low position, due to the shorter trajectory gravity creates.
With the arrow for example you aim six meters (+/-) above the height of target on the hill. Thats why military maps are important. You have to know the height-difference (and much much more) between an artillery piece and the target coordinates 😉 The video is about shooting at a short distance in a "straight" line. As the maker states....it's the basics...
How do you use this for aiming? If, let's say, the bullet drops 10cm from the distance I'm shooting - how do I know how high i need to aim in my scope?
Use the mil dots in the scope and distance form target. Say given a projectile velocity 1 mil dot represents 10 cm over a 100m distance, so aim up a dot. I`ll shoot a step-by-step math video on the actual mil dot calculation.
Its a similar concept for anti aircraft fire which takes an account of the moving aircraft and the speed of the projectile ... thus they always aim not at the aircraft but a distance ahead of it
Thanks for the tip. Without a video, here is how it goes: 1 estimate apparent speed of target, say 1 meter per second 2 calculate flight time based on projectile speed and distance to target, say 2 seconds 3 this gives us a lead of 2 m 4 based on distance to target and lead calculate lead angle (trigonometry), say 2 mil-dots Quite some work.
If you drop a 1lb ball and fire a 1lb ball at 30km per second 18.6411miles per second at the same time the ball you drop will hit the ground but the ball you fired will orbit the planet
im not smart ass but beofre i watch the vid. im gunah predict that its gunah have somthing to do with elevating your arrow above the target and point the arrow a few degreese to the left or right depending on the direction of wind.
+DEZiiRE_GH0sTy Lee Right. By exactly how much up depends on how long flight time takes. Air time is directly proportional to muzzle velocity and distance from target, so if those are known the aim correction can be calculated. Same with side wind.
Wow! Great, and thank you from Earth where our gravity is exact by definition to be 9.80665m/s/s at mean sea level and at 45 degrees latitude. I can see that you are from a much bigger planet where your gravity is 2x5.9= 11.8m/s/s and no atmosphere. Great video, though. FJB Out!