Subliminal

Not sure if i did it right. The sheet rotated in the second case but not in the first.

So does the whole plane rotate in example one? Also with the couple does the rotation occur about the point that is exactly the mid point of the two forces? Is it just a law based off of observation that objects rotate when the force is applied at a distance from the COM? Or can it be explained in terms of distribution of KE across the object? also what determines the axis of rotation is a force is applied at a non COM point of a uniform and non uniform bodies? I remember reading that the moment of a system can be calculated by the some of moments, is it something like that? I'm not sure why I find rotation so confusing.

So is F exerting a moment about points Q AND P in the first diagram with the moment about P equaling Fd and that about equaling F (some other perp d)? Also the moment of the couple does that only depend on the distance between the two forces? What are the forces acting on? Why does something rotate.

I understand one and two I don't understand number three, does it mean if a moment is acting about a point and something is placed on that point it too will turn? Btw can the two forces which make the couple act on the same point?

It was incorrect of me to say that, what I meant was tangential velocity • time, that is the linear displacement it would have experience if it escaped the circular path. I tried to use it to explain why tangential velocity equaled angular velocity ● radius before I knew it was cross multiplication occuring, I am still unsure if what kind of vector "r" represents, that was my original reason for thinking it was just a scaling device.

Hi, thanks again for the help so far. I was thinking about what you said and also did some more reasearch, this subject of moment has really been an issue whenever I studied physics. Does the moment increase with increasing radius because the angular momentum increases with a larger radius even for the same change in angular velocity? That is the change in tangential velocity is greater for the same change angular velocity if the radius is larger. I still don't really know what's going though, all I know is that more KE is transferred due to the increase in v, does that mean transferring energy is easier? If the radius is doubled the KE transferred is doubled and so the angular momentum is doubled meaning the torque was doubled..l Also you said that I shouldn't use "scaling" is that because cross multiplication was occuring and not dot multiplication?

Ah sorry for not replying in that thread, you did help me, though my understanding only took me this far, after some research I found that the vector system when torque and L are considered becomes three dimensional, and so I knew immediately that I had been thinking about the situation inaccurately, as I was using two dimensional systems. The reason I used the word "scaling" was because of the fact that the radius was basically the quotient of the arch length and so this waa carried through to the rest of the quantities, angular velocity and angular acceleration alike.

I'm using a circle diagram to derive the formulae for linear quantities in terms of angular ones. Radius r is used as a scaling device more than anything taken from the know formula for displacement in terms of angular displacement. radius × angular displacement = |linear displacement if object continued on linear trajectory, arch length| (radius × angular displacement)/time = radius×(angular velocity) = |linear velocity, tangential velocity to be precise| (Radius × (angular velocity))/time = radius × (angular acceleration) = tangential acceleration. radius × (angular velocity × mass) = radius × angular force = tangential force. Torque = r × tangential force(mv/t) = (r^2)× angular force?? (mw/t) Thus L = Iw, (I = (r^2 × mass) × angular velocity) Does the direction of the torque change during the resolution? Why is the tangential torque get scaled again? Edit: thread tittle should say why "is" tangential force scaled twice

L=vmr (angular momentum) If an object 'm' is moving and has a reference point 'p' that is a distance r from the object, is the angular momentum of the object its capacity to rotate a light plank fixed to point I know the torque is the change in angular momentum over time, but is L simply tangential velocity times mass times r or angular velocity times mass times r? I don't know what it is.... Angular velocity is theta/t = w, so is does L = wmr and not vmr?

What if you said "This is my machine it is designed to make a lot of sound, radiate heat, decompose over time" then your machine would be 100% efficient. I think non 100% efficiency means the forces that any machine uses are non conservative, or at least some of them are, that is mechanical energy (U+K) is not conserved.

Is if the path of the object is a circle I can use the circle as some sort of vector diagram and calculate the magnitude of the velocity using angular velocity as some sort of ratio and the radius as a scaling instrument? s = r theta, v = r w, a = r alpha, that sort of thing? I understand intuitively why linear displacement can be found this way, but i only understand mathematically why the other quantities are found. I suppose the further away a point is from the point of rotation the further it travels for a given change in theta, giving it a larger velocity than points which are closer, similarly a change in rate of ration would result in a bigger change in acceleration the magnitude of which would be determined by the points distance from the point of rotation. As for tangential acceleration, does this simply mean a decreases in the magnitude of T?

Angular displacement times r = |Linear displacement| (Intuitively I understand this but i can't put it into words, I know r*theata = L and if L = 0 then L after t seconds is the size of linear displacement t seconds after the object is released from the centripetal force) Angular displacement over time = |Linear velocity| (as the size of the velocity is constant and acceleration only changes the direction of the object) v = r*w, I would like to know what this means, when looking at a situation, what is the significance of it, can I express angular velocity in terms of angular velocity? Is, that the tangential velocity of an orbiting object is equal to distance traveled by the object over the time taken? One more thing, I learned that tangential acceleration is related to angular acceleration in the following way. a = r*alpha I'm not sure what this means as I thought that linear (tangential) velocity had to be constant for v = r*w to be true, so how can tangential acceleration (which would break the current circular path) Also expressing centripetal acceleration in terms of angular speed, I know how to do it, but i don't know what it means, it's significance. Also this looks quite close to the derivation of Kepler's third law, i just did this while messing around with equations, it probably means nothing, who knows. ac = v2/r w = v/r (linear - angular velocity rearranged) ac= (v/r)2/r ac= v2/r3