Calculating rifle movement as bullet reaches muzzle

[gunsandgunsmithing]

What my use of that equation has done is simply quantified the movement of the mass of the bullet and mass of powder, and equal movement of the mass of the rifle, which answers the original question. It may not be the most elegant way to go about it, but it seems to work. No?



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Equal movement? Wouldn't that require equal mass, bullet and rifle?

 

[TaperPin]

You've got to stop thinking that you can eliminate time because it's the same "dimension".
If we were able to do that, ALL the terms would drop out.

Momentum is mass times velocity; momentum is conserved.
Mass times distance is not conserved.

For an internal system without external forces moving it around, mass x distance is definitely conserved - the initial center of mass doesn’t move.

 

[TaperPin]

Equal movement? Wouldn't that require equal mass, bullet and rifle?

You’re correct, I misspoke. The mass x distance from the original center of mass is equalized. I went back and corrected it in the post.

 

[BoydAllen]

For an internal system without external forces moving it around, mass x distance is definitely conserved - the initial center of mass doesn’t move.

As the bullet travels down the barrel the force pushing it varies constantly and with that the cumulative movement. The total rifle movement would seem to be the sum of all of the incremental movements which varied with the pressure, hence the need for calculus.

 

[wwbrown]

As the bullet travels down the barrel the force pushing it varies constantly and with that the cumulative movement. The total rifle movement would seem to be the sum of all of the incremental movements which varied with the pressure, hence the need for calculus.

Nicely stated a better summary than mine, I wanted to start to get into the weeds to show there was a little more involved than TaperPin was implying. A summary like you have written probably provides others with a better understanding of the issues at hand.

 

[TaperPin]

Nicely stated a better summary than mine, I wanted to start to get into the weeds to show there was a little more involved than TaperPin was implying. A summary like you have written probably provides others with a better understanding of the issues at hand.

So you’re saying the basic principle of a stationary center of mass doesn’t apply?

 

[TaperPin]

As the bullet travels down the barrel the force pushing it varies constantly and with that the cumulative movement. The total rifle movement would seem to be the sum of all of the incremental movements which varied with the pressure, hence the need for calculus.

You’re trying to use energy calculations to answer a discussion about how a center of mass remains constant in a closed system.

As when a person walks down a canoe, their velocity doesn’t matter - as they travel down the canoe the total center of mass does not move - the canoe goes one way and the person goes the other, both at rates that preserves the initial state center of mass.

 

[davidjoe]

So you’re saying the basic principle of a stationary center of mass doesn’t apply?

I know I’m driving in the lane less travelled, but, if the bullet came to a sudden stop at the end of the barrel, that’s the only change that would be evident in the closed system, recentering of mass.

 

[wwbrown]

So you’re saying the basic principle of a stationary center of mass doesn’t apply?

Taper get a grip how can I be accused of saying something does not exist when I did not even mention it? Read what I wrote I never mentioned stationary center of mass as it does not apply to the rifle bullet system as it not an isolated system, you are sitting on he bench and there are forces acting on you that preclude you and the bullet from being an isolated system.

You mentioned you went hunting a lot instead of physics class that is your problem not mine and it is not my responsibility to fill in the gaps in your education. As such I am signing off from any responses to you.

Go back and read the last statement in one of responses to you about wisdom and take it to heart.

 

[TaperPin]

Taper get a grip how can I be accused of saying something does not exist when I did not even mention it? Read what I wrote I never mentioned stationary center of mass as it does not apply to the rifle bullet system as it not an isolated system, you are sitting on he bench and there are forces acting on you that preclude you and the bullet from being an isolated system.

You mentioned you went hunting a lot instead of physics class that is your problem not mine and it is not my responsibility to fill in the gaps in your education. As such I am signing off from any responses to you.

Go back and read the last statement in one of responses to you about wisdom and take it to heart.

We were ignoring friction on the bags, air friction, even assuming it was shot free recoil, now you say conservation of the center of mass can’t be used because of those things? That doesn’t sound consistent.

No, you didn’t mention a stationary center of mass, and now you’re ducking it completely, yet it sure seems to easily describe rifle movement, and using it to solve a real world issue matches within a few % of Quickload.

You can feel free to poo poo my education and knowledge of calculus all you want, I have thick skin and none of that bothers me in the slightest, but I’d love to hear your reasoning how a rifle doesn’t have a constant center of mass as the bullet travels down the barrel.

 

[xr650rRider]

When you get an Engineering degree, I know when we started differential equations, the professor stated, we had just gotten to the first math course that was beginning stages of being able to model/solve real world math problems. Everything was just simplified building blocks until then. The graduate level courses are where the real wizardry begins.

 

[xr650rRider]

Nothing linear there.

 

[BoydAllen]

You’re trying to use energy calculations to answer a discussion about how a center of mass remains constant in a closed system.

As when a person walks down a canoe, their velocity doesn’t matter - as they travel down the canoe the total center of mass does not move - the canoe goes one way and the person goes the other, both at rates that preserves the initial state center of mass.

Perhaps you need to spend more time in small boats. Back when I did, if I was slow and careful, the boat did not move at all in the opposite direction to the one I was moving in. You carry on about how simple it all is. If it is, do the calculations and post them and your answer. Actually I wrote about the way the pressure curve influences the barrels movement as the bullet goes down it. toward the muzzle, with the total movement just before the bullet clears the crown being the total of how much it moved during each small part of its travel. In other words, since the pressure is non linear, so is anything linked to it.

 

[jelenko]

Waste of time.

 

[TaperPin]

Perhaps you need to spend more time in small boats. Back when I did, if I was slow and careful, the boat did not move at all in the opposite direction to the one I was moving in. You carry on about how simple it all is. If it is, do the calculations and post them and your answer. Actually I wrote about the way the pressure curve influences the barrels movement as the bullet goes down it. toward the muzzle, with the total movement just before the bullet clears the crown being the total of how much it moved during each small part of its travel. In other words, since the pressure is non linear, so is anything linked to it.

I brought up a canoe because that’s a very common textbook example of a stationary center of mass of an independent closed system - it’s not something I made up - and velocity isn’t in any of the formulas for figuring center of mass that I’ve found.

Waste of time.

So you also believe a rifle doesn’t have a stationary center of mass as the bullet rolls down the barrel - and that junior high level center of mass calculations can’t be done without calculus?

I hope you expand on what you think happens to the center of mass - if I’m wrong I’ll gladly figure it another way. Heck, I’d learn to calculate it your way and give you credit every time the subject came up.

You have all the information for an example to compare with me and Quickload in posts #48 and #51 - go ahead and figure it your way and we’ll all get a look.

 

[TaperPin]

View attachment 1501816

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Nothing linear there

Many times as you guys want to keep bringing up the pressure curve, yes everyone on this forum knows it’s not linear, yet nobody has solved even a single simple example using it. Maybe this isn’t a good approach if nobody can use it? No?

The best and brightest minds in the country and only the country kid without any calculus can come close to a useable solution with junior high school algebra?

 

[TaperPin]

Taper get a grip how can I be accused of saying something does not exist when I did not even mention it? Read what I wrote I never mentioned stationary center of mass as it does not apply to the rifle bullet system as it not an isolated system, you are sitting on he bench and there are forces acting on you that preclude you and the bullet from being an isolated system.

You mentioned you went hunting a lot instead of physics class that is your problem not mine and it is not my responsibility to fill in the gaps in your education. As such I am signing off from any responses to you.

Go back and read the last statement in one of responses to you about wisdom and take it to heart.

I’m hoping to see your solution - all that real world problem solving.

 

[Bottom Fodder]

Maybe someone will come up with a phone app that will solve this riddle or an update to a Garman C1 that will. I know if I shoot my rifle free recoil the scope will hit my face I feel sure my face didn’t move forward pretty sure the rifle move rear ward but not sure during this when actually the bullet left the barrel,
after over a 100 post you would think those who need to know would have got the real answer

 

[Rat Rifle]

The answer to the original question is still in post #2 on this thread. Now, 117 posts later……..

 

[Joe Salty]

And like I've always said! Rifles are like women some like to be held tight, and some don't.

Joe Salty