Yes, based on CoE then the counter-weight would have a velocity of 2m/s using your 10 : 1 ratio.
The only way is to build a sim of it or take a video of a real life build and analyse it for KE/GPE gain over start conditions.
N.B. Please remember that physics sims may also operate from a Top Down approach i.e. make conditions fit CoE and Conservation of Momentum. I've been trying to find an answer to that for years but no luck yet.
energy producing experiments
Moderator: scott
re: energy producing experiments
A trebuchet needs no lever: smokin lamas and yo-yo de-spin devices are examples of no levers. You tube has a few.
Newton would predict a 10x launch velocity for a spinning ring that has a mass 10 times that of the missile. Don't forget that air resistance is massive for high speed objects.
Yes: this will be decided by quality high speed video cameras. Their cost is going down and quality is going up. Anybody have a favorite? My camcorder takes 30 frames per second and is blurry. I think sport action cameras take 240 frames per second and have a clear pictures, for only $300. It is time to visit Wal-mart.
Newton would predict a 10x launch velocity for a spinning ring that has a mass 10 times that of the missile. Don't forget that air resistance is massive for high speed objects.
Yes: this will be decided by quality high speed video cameras. Their cost is going down and quality is going up. Anybody have a favorite? My camcorder takes 30 frames per second and is blurry. I think sport action cameras take 240 frames per second and have a clear pictures, for only $300. It is time to visit Wal-mart.
Fletcher, what makes you doubt CoE and/or Conservation of Momentum?
Marchello E.
-- May the force lift you up. In case it doesn't, try something else.---
-- May the force lift you up. In case it doesn't, try something else.---
re: energy producing experiments
That's what my new thread will be about ME.
I currently have two problems to solve.
1. Which is most fundamental :- Conservation of Momentum (which I think it is) OR Conservation of Energy ?
i.e. If elasticity between colliding objects is 100% then both will be conserved, one as ... m v = F x t ... and the other as ... KE. I believe answering this will address some of the issues of hypothetical KE changes depending on reference frame.
2. What does the sim program predict and what path does it take to find the answer ?
i.e. From a 'Bottom Up' discreet approach where an answer trickles out the top, OR 'Top Down' approach which is more fuzzy and makes things conform to Conservation Laws by numerative iteration.
I have to prepare some sims of experiments to base the discussion around.
I currently have two problems to solve.
1. Which is most fundamental :- Conservation of Momentum (which I think it is) OR Conservation of Energy ?
i.e. If elasticity between colliding objects is 100% then both will be conserved, one as ... m v = F x t ... and the other as ... KE. I believe answering this will address some of the issues of hypothetical KE changes depending on reference frame.
2. What does the sim program predict and what path does it take to find the answer ?
i.e. From a 'Bottom Up' discreet approach where an answer trickles out the top, OR 'Top Down' approach which is more fuzzy and makes things conform to Conservation Laws by numerative iteration.
I have to prepare some sims of experiments to base the discussion around.
re: energy producing experiments
I guess a typical simulator does both, how else should it solve (=best match prediction within certain limits)?
<story>
I once build (read:tried to) a turbulent flow simulator, just because I like the swirls. There are several approaches, but the simplest one will make a good example, which is: treat a 2-D fluid like a collection of balls, all moving around, like an overcrowded billiard table.
So you can (hopefully) see that conservation of momentum is important, otherwise things can't flow. Equally important is the conservation of energy; this one is tricky because I found it quit difficult to not let it die out too quickly, or let it become unstable - several times that 'billiard-table' just blowed-up for no reason (or bad math). Then there is the timestep, the easiest is when one chooses a small number; not too small or it takes ages, and not too big because balls could occupy the same space or skip over another ball - loosing coherency, and (again) blow up the simulator.
</story>
You can see the same kind of quirks in WM2D.
I know it doesn't proof a thing, but it (c.o.momentum&energy) is the best explanation 'we' have on how things work.
As another example:
A dumb-bell falls to the ground at a certain angle, speed, rotation. At time(t1) one side is above ground, but at time (t2) it is below ground (while the other side is still above). It needs a correction: the velocity should be deflected, the new location should be somewhere above ground.. And in doing so it warps the connecting rod which shouldn't be that flexible, so that needs correction too; in the meantime rotation is also changed... This can't be discretely solved top-down, unless each and every situation is pre-formulated or otherwise is a very smart program.
hope that helped a bit?
add to story:Conservation of momentum on that 'billiard-table' is the most important thing in such a sim. So I guess agree with your hunch.
<story>
I once build (read:tried to) a turbulent flow simulator, just because I like the swirls. There are several approaches, but the simplest one will make a good example, which is: treat a 2-D fluid like a collection of balls, all moving around, like an overcrowded billiard table.
So you can (hopefully) see that conservation of momentum is important, otherwise things can't flow. Equally important is the conservation of energy; this one is tricky because I found it quit difficult to not let it die out too quickly, or let it become unstable - several times that 'billiard-table' just blowed-up for no reason (or bad math). Then there is the timestep, the easiest is when one chooses a small number; not too small or it takes ages, and not too big because balls could occupy the same space or skip over another ball - loosing coherency, and (again) blow up the simulator.
</story>
You can see the same kind of quirks in WM2D.
I know it doesn't proof a thing, but it (c.o.momentum&energy) is the best explanation 'we' have on how things work.
As another example:
A dumb-bell falls to the ground at a certain angle, speed, rotation. At time(t1) one side is above ground, but at time (t2) it is below ground (while the other side is still above). It needs a correction: the velocity should be deflected, the new location should be somewhere above ground.. And in doing so it warps the connecting rod which shouldn't be that flexible, so that needs correction too; in the meantime rotation is also changed... This can't be discretely solved top-down, unless each and every situation is pre-formulated or otherwise is a very smart program.
hope that helped a bit?
add to story:Conservation of momentum on that 'billiard-table' is the most important thing in such a sim. So I guess agree with your hunch.
Marchello E.
-- May the force lift you up. In case it doesn't, try something else.---
-- May the force lift you up. In case it doesn't, try something else.---
re: energy producing experiments
Yes. I built some simple experiments in sim world (I'm redoing them). They looked simple and the sim worked fine and popped out fine results. I decided that I should be able to calculate the answer long hand and get the same answers as the sim.
I eventually did formulate the equations to solve and find the answers the same as the sim. It took days and days as I applied different logic. When I sat back I realized that the simple sim actually gave a complex answer. And to me that answer (the equations I built) felt 'off'. They didn't feel right.
I want to see how you guys would build the equations, what you'd have in them, and what you think of mine ?
Your coding experience will be great ME, because as you've already outlined above you know that the real world is not steps of discrete inputs.
I eventually did formulate the equations to solve and find the answers the same as the sim. It took days and days as I applied different logic. When I sat back I realized that the simple sim actually gave a complex answer. And to me that answer (the equations I built) felt 'off'. They didn't feel right.
I want to see how you guys would build the equations, what you'd have in them, and what you think of mine ?
Your coding experience will be great ME, because as you've already outlined above you know that the real world is not steps of discrete inputs.
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eccentrically1
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The reason objects explode in simulations is because the precision is set greater than what the software can calculate, leading to rounding errors.
https://en.m.wikipedia.org/wiki/Physics ... imitations
https://en.m.wikipedia.org/wiki/Physics ... imitations
Nah, a standard 8 byte floatingpoint has a precision of 15 significant digits - most of the time the errors just average out; it's more like eehm 'greed' when choosing a 'realtime'-like timesteps, because of the velocity of things they eventually start to collide on the wrong side of eachother; correction leads to another unintended correction because in the meantime another (unrelated) object has taken that place... most of the time totally solvable by taking a smaller timestep.
re: energy producing experiments
That's right ME. That's how I solve it as well. Increase the accuracy. You have to do this if parts are moving fast for the reasons you said. If they are moving slow no problem with less accuracy.
In my scenario there were no collisions but I did use pulleys to interconnect objects. The sim spat out accelerations for all objects. When I took those accelerations and found velocities and thereafter mv and KE for these objects no surprise that they exactly conserved mv and KE.
I was astounded at the complex and somewhat non-linear equations I had to build long hand to reproduce those same sim accelerations.
This lead me to think that CoE was the most fundamental Law to be observed in sim world.
I still look at those equations (which work for all situations) and think that's 'odd'. But maybe it's explainable in a simple way that I didn't think about at the time ?
In my scenario there were no collisions but I did use pulleys to interconnect objects. The sim spat out accelerations for all objects. When I took those accelerations and found velocities and thereafter mv and KE for these objects no surprise that they exactly conserved mv and KE.
I was astounded at the complex and somewhat non-linear equations I had to build long hand to reproduce those same sim accelerations.
This lead me to think that CoE was the most fundamental Law to be observed in sim world.
I still look at those equations (which work for all situations) and think that's 'odd'. But maybe it's explainable in a simple way that I didn't think about at the time ?
re: energy producing experiments
ETA: I think in real world Momentum is the most fundamental Law from which KE follows and not the other way around as sim world appears to do.
That observation if true perhaps leaves the door open to manipulate system KE's towards OU outcomes.
That observation if true perhaps leaves the door open to manipulate system KE's towards OU outcomes.
If by momentum you mean Linear Momentum then I disagree.Fletcher wrote:ETA: I think in the real world Momentum is the most fundamental Law from which KE follows and not the other way around as sim world appears to do.
That observation if true perhaps leaves the door open to manipulate system KE's towards OU outcomes.
With linear momentum there is no datum. No point in space from which you can measure velocity. Two different observers moving apart will judge the momentum from their own frame of reference and therefore disagree on the momentum of a third body.
If by momentum you mean angular momentum then I agree.
With angular momentum there is a datum and that datum can easily be determined experimentally.
re: energy producing experiments
Well then Grimer .. I look forward to your input when my thread unfolds.
I'm definitely talking about Linear Momentum.
Angular is a given.
I'm definitely talking about Linear Momentum.
Angular is a given.
re: energy producing experiments
A one kilogram mass moving one meter per second has one and only one linear Newtonian Momentum; and this momentum is one.
If this same mass is caught on the end of a one meter string it will have an angular momentum of one.
If this same mass is caught on the end of a ten meter string it will have an angular momentum of ten.
When released from the string both masses can do the same amount of work or rise the same amount. So what meaning does angular momentum have? What meaning does a false concept have? What meaning does a false formula have?
There is no way to pretend that these formulas are the same: mv does not always equal mvr.
In the same way 1/2mv² does not equal mv. As the masses unwinds from the cylinder the linear momentum and the energy can not both remain constant. In the 10 to 1 the angular momentum conservation gives 3.16 m/sec and KE give 3.16 m/sec: but Newtonian momentum is 10 m/sec. You can not mix the two; one will be true and the other false.
If this same mass is caught on the end of a one meter string it will have an angular momentum of one.
If this same mass is caught on the end of a ten meter string it will have an angular momentum of ten.
When released from the string both masses can do the same amount of work or rise the same amount. So what meaning does angular momentum have? What meaning does a false concept have? What meaning does a false formula have?
There is no way to pretend that these formulas are the same: mv does not always equal mvr.
In the same way 1/2mv² does not equal mv. As the masses unwinds from the cylinder the linear momentum and the energy can not both remain constant. In the 10 to 1 the angular momentum conservation gives 3.16 m/sec and KE give 3.16 m/sec: but Newtonian momentum is 10 m/sec. You can not mix the two; one will be true and the other false.
Re: re: energy producing experiments
The actual trebuchet has the lever consisting of two parts - rigid and flexible.pequaide wrote:A trebuchet needs no lever: smokin lamas and yo-yo de-spin devices are examples of no levers. You tube has a few.
Newton would predict a 10x launch velocity for a spinning ring that has a mass 10 times that of the missile. Don't forget that air resistance is massive for high speed objects.
Yes: this will be decided by quality high speed video cameras. Their cost is going down and quality is going up. Anybody have a favorite? My camcorder takes 30 frames per second and is blurry. I think sport action cameras take 240 frames per second and have a clear pictures, for only $300. It is time to visit Wal-mart.
If the whole lever becomes flexible, on a string, for example, which can unwind, will the projectile speed be 10 to 1, if the length of the string to the distance to the centre of mass of the weight is 10 to 1???
re: energy producing experiments
Just from memory I would say that a 10 to one mass difference between the ring and the missile could achieve a stopped ring with a tether unwind from about half a circumference.
A circumference is 2 Pi r or 6.28 r so a 10 to 1 stop can be achieve with about a 3.15 r (4.15 r if you include the original radius) tether.
Full circumference unwinds will give you about a 40 to 1 for a stop.
A 10 r tether would probably be over 100 to 1(cylinder mass to missile mass) for a cylinder stop.
A circumference is 2 Pi r or 6.28 r so a 10 to 1 stop can be achieve with about a 3.15 r (4.15 r if you include the original radius) tether.
Full circumference unwinds will give you about a 40 to 1 for a stop.
A 10 r tether would probably be over 100 to 1(cylinder mass to missile mass) for a cylinder stop.