Science project

[gwalchmai]

My daughter is putting together a science project. She asked me for an idea and I (foolishly) recommended she explore the relationship between gravity and horizontal velocity. She liked the idea, so now I'm on the hook to help with technical details.

I recommended zeroing pistol sights at 25 yards and then varying the powder charge to show how the point of impact changes. She can include references to show how a bullet falls at a constant rate regardless of its velocity.

A chrono would be nice, and I may be able to get one, but if not she may be able to infer the velocity well enough based on charge weight.

And no, we will not have guns or boolits in the exhibit... ;)

Any thoughts, like suggestions of boolits and powders to accentuate the drop?

Thanks,
Miss Science's staff assistant

[nitesite]

One problem would be bolting down a barrelled action.

If you're using a handgun, even rested, won't the shorter or longer dwell times in the barrel affect impact on target? Slow sounds like it would exhibit more drop, but not if the muzzle rises a slightly higher amount than it does with a faster bullet.

I dunno... I'm the dumb guy here. I know there are some really sharp fellas here with engineering degrees who could mentor you thru.

Disregard.

[creophus]

A couple of questions, will the school frown upon using guns in a school project? If so, then that could effect her grade, even if there are no guns or bullets in the actual presentation.

How much drop will you see at 25 yards with a pistol? I'd try to stretch it out to 50 yards to get more data points.

Finally, I'm not sure what grade she's in, but this type of thing has already been done and can be found in a drop table. Gravity is constant regardless of horizontal velocity. A bullet fired at 10,000fps will hit the ground at the same time as a bullet with 0fps provided the height from which they are fired/dropped are the same.

[gwalchmai]

A couple of questions, will the school frown upon using guns in a school project? If so, then that could effect her grade, even if there are no guns or bullets in the actual presentation. I don't think so. I spoke with her teacher about the Science Fair and another parent said his kid is doing ballistics. The teacher said that was fine as long as no guns needed to be in the display.

How much drop will you see at 25 yards with a pistol? I'd try to stretch it out to 50 yards to get more data points.Good point.

Finally, I'm not sure what grade she's in, but this type of thing has already been done and can be found in a drop table. Gravity is constant regardless of horizontal velocity. A bullet fired at 10,000fps will hit the ground at the same time as a bullet with 0fps provided the height from which they are fired/dropped are the same. Thankfully, science projects do not have to be original research. The main goal is to demonstrate proficiency with the scientific method. (And to get her mom to let me buy a chronograph... ;))

[creophus]

Sounds like you got a green light all around! I'd recommend using a revolver as you will have greater opportunity to use light loads without worrying about functioning the slide.

You can also be sure to get a quality chrono with a wide range of velocity that it will read you know....since its for your daughter's science fair project.

[BoltNut]

If you can find a vice for the pistol to rest in (consistent barrel height)...you can probably get away with NOT using a chrono if you can show point of impact on a target dropping to certain levels based on powder and bullet differences. I'd almost suggest a heavy body 9mm for the range of loads available, and the ease of clamping it into a vice (say a Ruger P89, so something similar).

If you are an NRA member, there may be ballistic tables already calcualted for you to reference there, and compare your own results.

[Steve Koski]

Gwalch,

Relationship between gravity and horizontal velocity. Hmmmm.

Changing bullet drop seems more like it demonstrates the relationship between time of flight and bullet drop (or time and height). I suggest you use your estimated average velocities to guestimate the total bullet time of flight. Chart up the drop times and the bullet drop distances. You should get a nice curved line.

d1 = vot + (ag t2)/2

V0 is zero (or constant), so bullet drop should correlate with 1/2 A t^2

I wouldn't worry too much about bolting the gun down. Just use the same shooter in the same stance, aiming at the same point for every shot. This will keep V0 constant.

I think the project is gonna ROCK!!!

[creophus]

I'd also like to see numbers on how far the projectile would go before hitting the ground given the height at which each bullet was fired and their respective velocities. It'd be relatively easy to include while doing the other calculations.

[Tailgunner]

A bullet fired at 10,000fps will hit the ground at the same time as a bullet with 0fps provided the height from which they are fired/dropped are the same.

IF (and it's a big if) the barrel is level. Normaly when we shoot, the barrel is inclined upwards, launching the bullet on a parabolic arc that crosses the sight plane in 2 places (up close and again at the zero distance)

GWA
Revolver, perhaps in 38spl, spitting out wad cutter bullets and you'll want a 50yd range or better yet a 100yd'er that will allow you to see the impact point.
Chronographs are fairly inexpensive, and a couple of the companies sell "re-furbished" ones for 1/2-2/3 of their new ones. Be sure to keep the chrono far enough ahead of the muzzle that the blast gas dosn't effect the readings.
Now, if she realy want's to go "old school", a balistic pendulum would give impact energy, which can than be converted into impact velocity, but that won't provide you with the distance to impact information that her project is on. Hint, if she decides to do the pendulum thing, shoot into the endgrain of a minimum of 8x8x8 chunk of wood to prevent splitting and blow through

[nitesite]

You can plug all your data into Hornady's Ballistic Calculator and it does all the work for you.

http://www.hornady.com/ballistics/ballistics_calculator.php

[zdogk9]

Gwalch,

Relationship between gravity and horizontal velocity. Hmmmm.

Changing bullet drop seems more like it demonstrates the relationship between time of flight and bullet drop (or time and height). I suggest you use your estimated average velocities to guestimate the total bullet time of flight. Chart up the drop times and the bullet drop distances. You should get a nice curved line.

d1 = vot + (ag t2)/2

V0 is zero (or constant), so bullet drop should correlate with 1/2 A t^2

I wouldn't worry too much about bolting the gun down. Just use the same shooter in the same stance, aiming at the same point for every shot. This will keep V0 constant.

I think the project is gonna ROCK!!!

I just love it when you talk that insurance stuff!

[AlPackin]

I just love it when you talk that insurance stuff!
:animlol:

[yammerschooner]

The way it was demonstrated in my science class was with the use of a blow gun, an electromagnet, and a falling object. You probably all were introduced to the concept the same way, but I will outline it just in case kids were using a slide rule when some of you went to school.

When the projectile left the end of the barrel it cut an electrical circuit that ran an electromagnet on the other side of the room. When the electromagnet was cut off, it dropped a wadded up sock on the opposite side of the room that was held to the electromagnet because it had a chunk of metal taped to it. (So both objects began their downward acceleration at the same moment.)

You might want to go the blowgun route over the firearms route for a few reasons:


It can be performed repeatedly from within the confines of a classroom full of students.
The trajectory of the horizontally moving object is much more visible to the naked eye, since the dart might not hit the other falling object until both are near the floor.
A chrono can be used on the objects, and the mathematical calculations can be performed on an event that was witnessed in real life (as opposed to memorex).
Your daughter would have more hands-on input into setting up the actual experiment (and would have more opportunity to mess things up, which are where the real learning experiences happen since a hypothesis would have to be made to figure out what went wrong).
Parallels could then be drawn between the experiment and the same phenomenon happening with a bullet, explaining what is happening with the firearm in a clearer manner to those onlookers who might not be able to visualize the concept on something moving as fast as a bullet (which they cannot see the trajectory on).

Just my .02. I realize this probably isn't exactly what you are looking for, but figured it might help.

[Steve Koski]

That's pretty damned good for an english teacher.

[MakeMineaP99]

That's it, I'm turning in my engineer ring and going to teach english. Yammer and Koski have covered this very well. I have nothing to add.

[gwalchmai]

Thanks, guys. It's a-percolatin'...

[VN350X10]

Dan, I'm right behind you !
The blowgun idea would have pulled a easy "A" from old Mr. Prez, head of the Science Dept. when I was in high school.
And yes, as a matter of fact, I DID use a slide rule ! A good "Nerd Sword" still comes in handy, just to mess with the heads of the "newbies" who have never seen one.

uncle albert