Buell Dynamics Problem!
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dang it I have done too much statics laity and am stumped without theta (my math fu is too weak to extrapolate around my trig and solve down. and I haven't touched calc in over 6 years so its WAY too rusty)
I love me some physics but just don't have the extra time to study it anymore.
I have so many physics problems and questions right now and no way to answer all of them [mad][mad]
drifting you make me so jealous sometimes!!
lol
I love me some physics but just don't have the extra time to study it anymore.
I have so many physics problems and questions right now and no way to answer all of them [mad][mad]
drifting you make me so jealous sometimes!!
lol
driftingswiftly
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Well BRatigan, you managed to completely perplex me. Hahaha. I don't know what you're talking about.
Delta, that is the angular rate of the frame with respect to the inertial frame. It is a little confusing the way I drew it so close to the wheel tho.
Twisted and Wall, you are right, but that doesn't matter in this problem for two reasons. 1) Its covered in the assumptions. 2) (The real reason) It is only dealing with an instantaneous velocity. To solve further, all acceleration level values and accompanying parameters would be needed: accelerations, torques, inertias, rotational inertias, etc. Also, the problem gets big real fast when you make that jump. This is a very basic problem and it would expand about 4-5 times as long. Much too long for a side example that isn't directly related to an orbital dynamics lecture, lol.
You guys are on point with this mess! Im impressed.
Delta, that is the angular rate of the frame with respect to the inertial frame. It is a little confusing the way I drew it so close to the wheel tho.
Twisted and Wall, you are right, but that doesn't matter in this problem for two reasons. 1) Its covered in the assumptions. 2) (The real reason) It is only dealing with an instantaneous velocity. To solve further, all acceleration level values and accompanying parameters would be needed: accelerations, torques, inertias, rotational inertias, etc. Also, the problem gets big real fast when you make that jump. This is a very basic problem and it would expand about 4-5 times as long. Much too long for a side example that isn't directly related to an orbital dynamics lecture, lol.
You guys are on point with this mess! Im impressed.
driftingswiftly
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Haha, I was wondering who posted that pic!
Id like to point out a few things if i may. Phi is a function of time, so it will be changing according to w_{B/A}, which is assumed constant at that moment. Also, because this is a 2-D problem, there are no times where v ant=v bike. This is because the wheel is spinning. Also, r for the rear wheel actually isn't needed.
You def have a pretty solid grasp on the problem tho!
Also, I want to reiterate to everyone that this isn't a problem solving for the equations of motion of a firebolt doing a wheelie. Depending on the assumptions, that can be a massive project.
Id like to point out a few things if i may. Phi is a function of time, so it will be changing according to w_{B/A}, which is assumed constant at that moment. Also, because this is a 2-D problem, there are no times where v ant=v bike. This is because the wheel is spinning. Also, r for the rear wheel actually isn't needed.
You def have a pretty solid grasp on the problem tho!
Also, I want to reiterate to everyone that this isn't a problem solving for the equations of motion of a firebolt doing a wheelie. Depending on the assumptions, that can be a massive project.
yea but I like the motion of the firebolt more, its along the lines of what I used to do for fun.
relative to the ground in multi vector set up with only an instantaneous glimpse v ant = v bike for the x axis only. sorry I didn't label it well enough. it should have read V ant x = v bike
I always set up in multi vector to 90 degree vectors on an axis then to a single vector
but maybe I am still wrong? I am VERY rusty still
but I love looking at this problem because I am getting exited about physics all over again and trying to figure out all the levels needed to solve it even if I can no longer remember how to
relative to the ground in multi vector set up with only an instantaneous glimpse v ant = v bike for the x axis only. sorry I didn't label it well enough. it should have read V ant x = v bike
I always set up in multi vector to 90 degree vectors on an axis then to a single vector
but maybe I am still wrong? I am VERY rusty still
but I love looking at this problem because I am getting exited about physics all over again and trying to figure out all the levels needed to solve it even if I can no longer remember how to
driftingswiftly
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You're right if the bike had both wheels on the ground, or it the wheelie angle was constant (assuming a no slip condition rotational rate o the front wheel). But, assuming the same front wheel angular rate, for a rising wheelie the point of = x velocities actually wouldn't be when the ant is at the bottom of the wheel. Just like if you have a moving horizontal rod that you rotate to stand on end. During the rotation, the x velocity component of the leading edge of the rod is actually less than the rod's center of mass.
This is one of my fave threads! haha i love it.
This is one of my fave threads! haha i love it.
Right no rising rate is calculated there
I see 3 systems
1 motorcycle velocity
2 motorcycle rise rate
3 front wheel spin
But I assumed that front wheel rotation was equal to rear wheel rotation
For ant = bike I was using the same principal as a tire on the road
The bottom of the tire has 0 speed relative to the road
The top has 2x the relative speed of the system
And both front and rear are equal to the system
Everything between these key points can be calculated based off of these constants and some trig
Or so I thought I remembered...
Still wrong?
Just in case it comes off as an argument it's not, I am really enjoying the physics lesson
I see 3 systems
1 motorcycle velocity
2 motorcycle rise rate
3 front wheel spin
But I assumed that front wheel rotation was equal to rear wheel rotation
For ant = bike I was using the same principal as a tire on the road
The bottom of the tire has 0 speed relative to the road
The top has 2x the relative speed of the system
And both front and rear are equal to the system
Everything between these key points can be calculated based off of these constants and some trig
Or so I thought I remembered...
Still wrong?
Just in case it comes off as an argument it's not, I am really enjoying the physics lesson
driftingswiftly
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Oh yeah, i know its not an arguement. haha This is what I do everyday, discuss problems.
Ok, so yes, again, That is right if the wheelie is being held at the same angle (of which a special case is 0 aka 2 wheels on the road). But the "rise rate" isn't actually that. its a rotational rate of the bike. So as soon as the bike rotates above level riding, there will be a small component in the x direction that is caused by the while bike rotating back. This component is actually in the negative direction, so in the case of the ant at the bottom of the wheel, it would actually have a negative velocity with respect to the road....because its zero for the level case, and only that one affect is in play. This Assuming our constant rates and everything, this component will only be a function of the wheelie angle phi...and time bc phi is a function of time.
Ok, so yes, again, That is right if the wheelie is being held at the same angle (of which a special case is 0 aka 2 wheels on the road). But the "rise rate" isn't actually that. its a rotational rate of the bike. So as soon as the bike rotates above level riding, there will be a small component in the x direction that is caused by the while bike rotating back. This component is actually in the negative direction, so in the case of the ant at the bottom of the wheel, it would actually have a negative velocity with respect to the road....because its zero for the level case, and only that one affect is in play. This Assuming our constant rates and everything, this component will only be a function of the wheelie angle phi...and time bc phi is a function of time.
and that's where your physics fu is so much stronger than mine because I need to take the rise of the bike as a separate system and one it is solved down add it to the tire system. (rise will be +Y -X) If I were to try and do it at the same time all would go wrong.
or does this problem need to be handled all at once?
I also know that I can only do instantaneous moments for anything rotational. I lack the knowledge to write it out as a moving object
ok one that has bothered me for a while that none of my physics profs could ever answer is:
what is the force (or principal/law of supporting evidence) that holds two pieces of glass together with water in between them?
how does one calculate that force and quantify it?
all I have heard is suction, but have never found any formula or rule to calculate the force. (well actually the maximum potential force because the force it applies holding them together will be equal to the force pulling them apart if they are static)
I would expect that cohesion as well as adhesion would need to be given values as well as the surface area of the two pieces of glass?
what about when the glass is not lifted uniformly?
can the "breaking point" be determined mathematically based off of the distance separating the pieces of glass or the force attempting to separate them?
is the force centralized and radiating from the center or is it uniform?
help me Obiwan Kenobi you're my only hope
or does this problem need to be handled all at once?
I also know that I can only do instantaneous moments for anything rotational. I lack the knowledge to write it out as a moving object
ok one that has bothered me for a while that none of my physics profs could ever answer is:
what is the force (or principal/law of supporting evidence) that holds two pieces of glass together with water in between them?
how does one calculate that force and quantify it?
all I have heard is suction, but have never found any formula or rule to calculate the force. (well actually the maximum potential force because the force it applies holding them together will be equal to the force pulling them apart if they are static
)I would expect that cohesion as well as adhesion would need to be given values as well as the surface area of the two pieces of glass?
what about when the glass is not lifted uniformly?
can the "breaking point" be determined mathematically based off of the distance separating the pieces of glass or the force attempting to separate them?
is the force centralized and radiating from the center or is it uniform?
help me Obiwan Kenobi you're my only hope
driftingswiftly
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Yes this problem does have to be solved all together and as a function that is instantaneously accurate for all time, but not continuously bc we would have to go to the acceleration level.
For your glass problem. The reason you have never gotten a clear simple answer is that there is not one. This is a result of many different physical phenomena all interacting. As a result, its also a function of many different variables even though the system seems simple. Some of the affects in play are capillary action, surface tension, vacuum (suction), van der Waals force, etc. Some of the variables it will depend on are temperature, viscosity of whatever fluid is being oreo-ed, glass texture, atmospheric conditions, surface area, separation distance, stiffness of glass...and many more. This is actually a really sensitive system and if you wanted to be really pedantic you would have to get into things like color, translucence, latitude, magnetic field...
No, the force would not be uniform, even if it was pulled by an evenly distributed load, because of end effects. It would be given a uniform load and infinite plates and blah blah blah ideal conditions.
Yes, it is very sensitive to how uniform it is lifted. No, an accurate breaking point could not be determined because it is so unstable and dependent on things that are beyond the accuracy of most measurement tools. Also, lifting them consistently and uniformly would also be a problem.
If everything was polished and carefully measured and whatever, my guess is that there would still be some perturbation that would cause uneven loading and everything to go unstable. A fat girl walking down an adjacent hall is a good example of what might cause such a perturbation.
If you look hard enough you could probably find some oversimplified idealized equation that some professor with a dying career tried to pass off. However, it will not be accurate because there is a good chance hes overweight.
For your glass problem. The reason you have never gotten a clear simple answer is that there is not one. This is a result of many different physical phenomena all interacting. As a result, its also a function of many different variables even though the system seems simple. Some of the affects in play are capillary action, surface tension, vacuum (suction), van der Waals force, etc. Some of the variables it will depend on are temperature, viscosity of whatever fluid is being oreo-ed, glass texture, atmospheric conditions, surface area, separation distance, stiffness of glass...and many more. This is actually a really sensitive system and if you wanted to be really pedantic you would have to get into things like color, translucence, latitude, magnetic field...
No, the force would not be uniform, even if it was pulled by an evenly distributed load, because of end effects. It would be given a uniform load and infinite plates and blah blah blah ideal conditions.
Yes, it is very sensitive to how uniform it is lifted. No, an accurate breaking point could not be determined because it is so unstable and dependent on things that are beyond the accuracy of most measurement tools. Also, lifting them consistently and uniformly would also be a problem.
If everything was polished and carefully measured and whatever, my guess is that there would still be some perturbation that would cause uneven loading and everything to go unstable. A fat girl walking down an adjacent hall is a good example of what might cause such a perturbation.
If you look hard enough you could probably find some oversimplified idealized equation that some professor with a dying career tried to pass off. However, it will not be accurate because there is a good chance hes overweight.
there are a few answers to this with my own given values:
1. all velocities must be close to zero since the ant is still on the wheel, and a Buell should be going much faster.
2. Building on that and using the problem solving logic from one of my old professors, you always start with canceling out variables in the equation that are close to zero. In this equation I'd say the ant has no mass, so it's inertia would also cancel out. So my answer would be zero.
3. Just like Dave said earlier in the post, it has been way too long since I dusted off math of any type... makes me wonder where my education went.. oh well, the piece of paper did it's job...
1. all velocities must be close to zero since the ant is still on the wheel, and a Buell should be going much faster.
2. Building on that and using the problem solving logic from one of my old professors, you always start with canceling out variables in the equation that are close to zero. In this equation I'd say the ant has no mass, so it's inertia would also cancel out. So my answer would be zero.
3. Just like Dave said earlier in the post, it has been way too long since I dusted off math of any type... makes me wonder where my education went.. oh well, the piece of paper did it's job...
driftingswiftly
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haha, your professor sounds ... interesting? Yeah, ill use the word interesting. But yeah, mass/inertia is not needed to solve this problem.
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