6
votes
Accepted
Centrepetal force at the north or south pole
You have made a very common error. $v$ varies with $r$; $\omega$ does not. Therefore, as $r\to0$, $a=r\omega^2\to 0$ as well.
- 58.1k
2
votes
The No Slip/Slip Condition for Rotating/Rotating and Translating Bodies
Is it correct to say that if $v≠ωr$, slip will occur
yes
where if $v<ωr$ the sphere will rotate "too fast"
yes
where if $v>ωr$ the sphere will slip?
yes
Does the direction of ...
- 9,865
2
votes
Why is the direction of friction inwards in a rotating disc even though there is no motion in the inward direction?
However, previously I had learnt that friction acts in a direction
opposite to the direction of motion
That applies to kinetic friction which acts opposite to relative motion that is underway between ...
- 75.6k
2
votes
Physical Significance of Torque
If torque about O is non zero,there is rotational effect of Force and hence the body is rotating about O.
Maybe, maybe not. We can say that the angular momentum about that point is changing. ...
- 41.9k
1
vote
What does the double covering in the Dirac equation have to do with that of $SO(3)$ by $SU(2)$?
Hestenes modifies the Dirac equation in order to identify the Dirac spinor's 8 real components with those of the even spacetime algebra. I think that's wrong, because it's incompatible with the fact ...
- 28.1k
1
vote
Centripetal force
i am the observer at ground watching the stuff and i noticed that bob
is rotating as well as rising ( thread making some angle with
vertical)
Since the thread is at some angle from vertical, the ...
- 7,398
1
vote
Accepted
Why is the direction of friction inwards in a rotating disc even though there is no motion in the inward direction?
Since you confused about relative motion between the thing ($m$ at $R$) on the disc (spinning at $\omega$), let's solve it in a rotating frame so that every thing is at rest $(v=0)$, it's a statics ...
- 36.6k
1
vote
Why is the direction of friction inwards in a rotating disc even though there is no motion in the inward direction?
Friction acts opposite of the direction of relative motion if friction wasn't there.
In the absence of friction an object placed on a rotating disk (carefully to match the velocity of the object on ...
- 3,220
1
vote
Accepted
Cartesian tensor transformation and representations of $SO(3)$
The question is very unclear so maybe what the OP means is that any matrix
$$
M=\pmatrix{M_{xx}&M_{xy}&M_{xz}\\ M_{yx}&M_{yy}&M_{yz}\\ M_{zx}&M_{zy}&M_zz}
$$ can be written in ...
- 46.8k
1
vote
The No Slip/Slip Condition for Rotating/Rotating and Translating Bodies
$\dots$ can this be extended to an accelerating system by taking the derivative with respect to time on both sides $\dots$ - yes
In the first three examples on the left, the friction force to the ...
- 98.6k
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