We could use a laser and meassue the deflection of the beam, use an accelerometer or use a glass of water amd measure the difference in water level across the glass. Is that enough?
The Swing of a Pendulum
- Thread starter Motor Daddy
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We could use a laser and meassue the deflection of the beam, use an accelerometer or use a glass of water amd measure the difference in water level across the glass. Is that enough?
Motor Daddy
Valued Senior Member
How about we start from scratch and run through the concept step by step nice and slow, shall we??
You didn't convince anyone the first 50 times do you really think 51 times is the charm?
Motor Daddy
Valued Senior Member
No, obviously he's gonna back out long before he admits he's wrong. I want to start from scratch. There is a stick. How long is the stick?
Motor Daddy
Valued Senior Member
Can you convert to light seconds please?
Simplest one would be to observe a mass floating free in the center of the ship. If it doesn't stay there - the rocket is accelerating.
Yes. Let me know when you've read and worked through a high school mechanics/kinematics textbook. Then you'll actually have some grasp of what an inertial frame is. Until you have done that or can demonstrate a working understanding of what an inertial frame is you are incapable of having an informed rational discussion on this subject matter.
Motor Daddy
Valued Senior Member
Why do I have to play by your rules?
I'll tell ya what, we'll play the game twice if you like. The first time we play by my rules and the second time we play by your rules. If the first time we play you decide you are losing and decide to drop out you forfeit and hence no need for a second game, I win. If I decide that I've taken just about as much ass whoopin from you as one man could possibly stand, and I drop out, then you win, hence no need for a second game. Of course, if the first game runs the course (round 1) and both of us continue to be in the game then we will play round 2. The same rules apply concerning forfeit. If both games run the course and neither of us has quit, then we will have to assume to just agree to disagree.
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Motor Daddy
Valued Senior Member
The only thing you have is relative velocity. Now you simply added an additional relative velocity, the relative velocity between the ship and the floating mass. You did not show an acceleration in the unit m/s^2.
If you do not understand what an inertial frame is then how can we have a discussion about them and their place within relativity or notions of absolute inertial frames? Is that unreasonable? You are demonstrably ignorant of the subject matter you want to talk about, thus rendering discussion difficult or even impossible. People such as JamesR have tried to spoon feed you and you don't want to listen. As such I'm not going to do it for you, you need to do it for yourself. If you don't respect yourself enough to be informed on a subject before asserting things about it then why should anyone else give you any respect?
If you think I'm being unreasonable then so be it. I happen to care about truth and honesty, even if you don't.
Motor Daddy
Valued Senior Member
What a load of crap!
Motor Daddy
Valued Senior Member
This is how acceleration works in the absolute frame:
Motor Daddy
Valued Senior Member
Just for the record AN, why did you pass up the chance to prove me wrong on the torque and HP example? Didn't feel up to the challenge of defending your science using that example?
Motor Daddy:
Clearly, trying to discuss pendulums in accelerating cars is way too complex a problem for you to cope with at this stage. So, let me just go back over the whole relative-velocity problem you were having earlier in the thread.
First, let's dispense with the confusion about whether we're talking one or two velocities. To specify a relative velocity, we always need two velocities. The velocity of object B relative to object A is always defined to be:
$$v_{rel} = v_B - v_A$$
So, if we say that car B is travelling 20 m/s faster than car A we have:
$$20 = v_B -v_A$$
Notice that this tells us nothing about the velocities of cars A and B, other than that one is 20 m/s greater than the other. Thus, it is possible that
$$X: v_A = 0, v_B=20$$
or
$$Y: v_A=80, v_B=100$$
or whatever.
What about this:
$$Z: v_A=-10, v_B=10$$
?
This is also fine.
"What's with the X,Y, and Z?", I hear you ask. X,Y and Z are what we call reference frames. I'm sure you remember the definition of a reference frame from our many previous discussions (think sticks and clocks etc. - remember?)
When we say "Car B is travelling 20 m/s faster than Car A" we haven't explicitly specified any particular reference frame. And until we do, we can't assign numbers to the velocities of cars A and B. One important caveat, of course, is that we do require a pre-existing concept of what a metre and a second are, or else the expression "20 m/s faster" is itself meaningless. But that's basic common sense.
Yes. Each of these situations corresponds to a different choice of reference frame.
This raises a slight complication.
$$W: v_A=-15, v_B=5?$$
In that case, B's velocity relative to A is still 20 m/s, but can we say that B is travelling faster than A? Clearly, in this particular choice of reference frame, the magnitude of the velocity (i.e. the speed) of B is less than the speed of A, but that does not change the fact that the velocity of B relative to A is still 20 m/s.
So, if you're having issues with "B is going faster than A", then I suggest you do not choose a frame such as frame W in the above example. You're better off working in a simple frame, and the simplest one to choose is the one where:
$$v_A = 0, v_B = 20$$
That way, you won't tie yourself in mental knots trying to work it all out.
Right. A relative velocity assumes that we have already established a notion of what we mean by the term "velocity", because relative veloocity is just the difference between two velocities.
I hope that's sorted now to your satisfaction. If you have any questions, please ask.
There's nothing absolute about that. In the rest frame of the sphere that always happens, whether or not the sphere is moving in some other reference frame.
Where did this "direction" idea of yours come from? It sounds like you're assuming some frame of reference prior to the information you have given. In a particular given frame, we presumably know the velocity of at least one of the rockets. Then, observing that the distance between the two is increasing allows us to deduce the direction of travel of the other rocket in that given frame.
Sure. It's just a matter of picking the right frame of reference.
Hope this helps!
Clearly, trying to discuss pendulums in accelerating cars is way too complex a problem for you to cope with at this stage. So, let me just go back over the whole relative-velocity problem you were having earlier in the thread.
First, let's dispense with the confusion about whether we're talking one or two velocities. To specify a relative velocity, we always need two velocities. The velocity of object B relative to object A is always defined to be:
$$v_{rel} = v_B - v_A$$
So, if we say that car B is travelling 20 m/s faster than car A we have:
$$20 = v_B -v_A$$
Notice that this tells us nothing about the velocities of cars A and B, other than that one is 20 m/s greater than the other. Thus, it is possible that
$$X: v_A = 0, v_B=20$$
or
$$Y: v_A=80, v_B=100$$
or whatever.
What about this:
$$Z: v_A=-10, v_B=10$$
?
This is also fine.
"What's with the X,Y, and Z?", I hear you ask. X,Y and Z are what we call reference frames. I'm sure you remember the definition of a reference frame from our many previous discussions (think sticks and clocks etc. - remember?)
When we say "Car B is travelling 20 m/s faster than Car A" we haven't explicitly specified any particular reference frame. And until we do, we can't assign numbers to the velocities of cars A and B. One important caveat, of course, is that we do require a pre-existing concept of what a metre and a second are, or else the expression "20 m/s faster" is itself meaningless. But that's basic common sense.
Yes. Each of these situations corresponds to a different choice of reference frame.
This raises a slight complication.
$$W: v_A=-15, v_B=5?$$
In that case, B's velocity relative to A is still 20 m/s, but can we say that B is travelling faster than A? Clearly, in this particular choice of reference frame, the magnitude of the velocity (i.e. the speed) of B is less than the speed of A, but that does not change the fact that the velocity of B relative to A is still 20 m/s.
So, if you're having issues with "B is going faster than A", then I suggest you do not choose a frame such as frame W in the above example. You're better off working in a simple frame, and the simplest one to choose is the one where:
$$v_A = 0, v_B = 20$$
That way, you won't tie yourself in mental knots trying to work it all out.
Right. A relative velocity assumes that we have already established a notion of what we mean by the term "velocity", because relative veloocity is just the difference between two velocities.
I hope that's sorted now to your satisfaction. If you have any questions, please ask.
There's nothing absolute about that. In the rest frame of the sphere that always happens, whether or not the sphere is moving in some other reference frame.
Where did this "direction" idea of yours come from? It sounds like you're assuming some frame of reference prior to the information you have given. In a particular given frame, we presumably know the velocity of at least one of the rockets. Then, observing that the distance between the two is increasing allows us to deduce the direction of travel of the other rocket in that given frame.
Sure. It's just a matter of picking the right frame of reference.
Hope this helps!
There are no absolutes in spacetime. No origin, no zero, no ground, no reference.
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If you feel that intellectual honesty and knowing what the meaning of words are before using are 'a load of crap' then so be it. You simply prove you are not worth anything other than ridicule.
You have zero evidence reality works like that.
Nice attempt to change the subject away from the fact you've had your pendulum assertions demolished. In doing so it was shown you don't even know what an inertial frame is, thus undermining your claims about pretty much anything else. If you cannot even describe properly motion, don't grasp kinematics and don't understand what an inertial frame is then, as shown repeatedly, you're incapable of even discussing such things as momentum, velocity and torque.
I asked you for evidence for your claims, you just repeated your assertions. I correct your ignorant on what inertial frames are, you continue to repeat a debunked assertion. I comment that understanding the meaning of words is necessary to discuss them and you call it 'a load of crap'. All point to the complete lack of honesty on your part.
Tell you what. If you can formally, ie using mathematics, describe the torque scenario you have previously attempted to discuss, then I'll discuss it with you. This is not asking much, it just requires you can do mathematics expected of 15 or 16 year olds. If you cannot do this then you are illustrating you lack sufficient capabilities to even present a 'challenge' to mainstream physics, never mind demonstrate it to be a valid challenge.
I'm willing to discuss things with you if you can demonstrate you're even at the level of a child when it comes to understanding what you want to discuss. If you cannot reach this minimal level then any time spent is likely to be wasted on you, due to your inability to comprehend. If all you can say is "What a load of crap" then you're little more than trolling.
No Absolutes
There are no absolutes in spacetime. No origin, no zero, no ground, no reference.
There is no absolute position in space. There is no absolute zero time.
There can be no absolute velocity or acceleration without absolute position.
Evidence:
Constant velocity is the invariant change in spatial position with respect to time.
Change in linear position: Δx = x[sub]1[/sub] - x[sub]0[/sub];
► x[sub]0[/sub] is the origin from which the change in position is measured. Relative.
Change in time: Δt = t[sub]1[/sub] - t[sub]0[/sub];
► t[sub]0[/sub] is the time origin at which x[sub]0[/sub] was the position. Relative.
Constant velocity: the rate of change in position: v = Δx/Δt
► v = Δx/Δt = (x[sub]1[/sub] - x[sub]0[/sub]) / (t[sub]1[/sub] - t[sub]0[/sub]). Relative.
Generalized Euclidean distance:
r = √ (x[sub]1[/sub] - x[sub]0[/sub])² + (y[sub]1[/sub] - y[sub]0[/sub])² + (z[sub]1[/sub] - z[sub]0[/sub])²
► x[sub]0[/sub], y[sub]0[/sub], and z[sub]0[/sub] are relative. r is relative.
Constant velocity in 3-space: v = Δr / Δt. Relative.
By the same logic, there is no absolute for all cases of variable velocity (acceleration).
Conclusion: acceleration is relative.
Conclusion: As there is no absolute position in spacetime, there can be no absolute velocity or acceleration.
Further application of the same logic, and any effort to derive the expressions for mechanics, will produce the same result: the laws of physics, are relative.
There are no absolutes in spacetime. No origin, no zero, no ground, no reference.
There is no absolute position in space. There is no absolute zero time.
There can be no absolute velocity or acceleration without absolute position.
Evidence:
Constant velocity is the invariant change in spatial position with respect to time.
Change in linear position: Δx = x[sub]1[/sub] - x[sub]0[/sub];
► x[sub]0[/sub] is the origin from which the change in position is measured. Relative.
Change in time: Δt = t[sub]1[/sub] - t[sub]0[/sub];
► t[sub]0[/sub] is the time origin at which x[sub]0[/sub] was the position. Relative.
Constant velocity: the rate of change in position: v = Δx/Δt
► v = Δx/Δt = (x[sub]1[/sub] - x[sub]0[/sub]) / (t[sub]1[/sub] - t[sub]0[/sub]). Relative.
Generalized Euclidean distance:
r = √ (x[sub]1[/sub] - x[sub]0[/sub])² + (y[sub]1[/sub] - y[sub]0[/sub])² + (z[sub]1[/sub] - z[sub]0[/sub])²
► x[sub]0[/sub], y[sub]0[/sub], and z[sub]0[/sub] are relative. r is relative.
Constant velocity in 3-space: v = Δr / Δt. Relative.
By the same logic, there is no absolute for all cases of variable velocity (acceleration).
Conclusion: acceleration is relative.
Conclusion: As there is no absolute position in spacetime, there can be no absolute velocity or acceleration.
Further application of the same logic, and any effort to derive the expressions for mechanics, will produce the same result: the laws of physics, are relative.
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(Mods: thank you. My editing ability is restored.)
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