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In this system, how can you determine which direction it will rotate?
 one year ago
 one year ago
In this system, how can you determine which direction it will rotate?
 one year ago
 one year ago

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geerky42Best ResponseYou've already chosen the best response.1
Like, if \(m_1\) is larger than \(m_2\), how can you tell which way it will rotate?
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
Sorry for keeping asking you for help, but can you answer this question, @shubhamsrg ?
 one year ago

shubhamsrgBest ResponseYou've already chosen the best response.2
Product of mr will decide that
 one year ago

shubhamsrgBest ResponseYou've already chosen the best response.2
Clockwise torque = (m2)g(r2) ANti clockwise torque = (m1)g(r1) Greater torque will prevail
 one year ago

shubhamsrgBest ResponseYou've already chosen the best response.2
Also, am assuming its a massless pulley , right ?
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
Well, the problem I'm currently working on, it doesn't say anything about the mass of pulley... but it does say that the combined moment of inertia of the two wheels is 2.7 kg·m². So pulley or wheels has mass?
 one year ago

shubhamsrgBest ResponseYou've already chosen the best response.2
Yes pulleys has mass.
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
The reason I ask this question is because I want to set up a sum of force for both two masses correctly and I don't know which to go first; mg or T (tension)
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
If mass goes upward, T goes first, otherwise, m·g goes first.
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
My attempt is to set up some equations then do some substitution and isolate and find \(\alpha\) in term of variables that already have given value. I don't know if this can work.
 one year ago

shubhamsrgBest ResponseYou've already chosen the best response.2
Well simply write eqn of rotation.
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
\(\sum \tau = T_1R_1  T_2 R_2 = I\alpha\) OR \(\sum \tau = T_2R_2  T_1 R_1 = I\alpha\) It depends which direction it rotates... I also need to find two tensions...
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
\[\sum F_1 = m_1g  T_1 = m_1 a\] OR \[\sum F_1 = T_1  m_1g = m_1 a\] \[\sum F_2 = m_2g  T_2 = m_2 a\] OR \[\sum F_2 = T_2  m_2g = m_2 a\] That's why I need to determine which direction it rotates...
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
Any ideas? "Clockwise torque = (m2)g(r2) ANti clockwise torque = (m1)g(r1) Greater torque will prevail" This works only if pulley is massless, right?
 one year ago

shubhamsrgBest ResponseYou've already chosen the best response.2
You can take any direction to be +ve. If your assumption would be wrong, it'll automatically come to be ve
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
Ugh, I hope I make right guess first, lol.
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
What is angular acceleration is negative? How can I know if my assumption is right or wrong?
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
Problem asks me to "take clockwise direction as positive."
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
Wait, angular acceleration cannot be negative, right?
 one year ago

shubhamsrgBest ResponseYou've already chosen the best response.2
It is a vector, it can be negavtive, ve will just denote the direction.
 one year ago

shubhamsrgBest ResponseYou've already chosen the best response.2
The linear acceleration of both masses will not be equal
 one year ago

shubhamsrgBest ResponseYou've already chosen the best response.2
m1g  T1 = m1 a1 T2  m2g = m2 a2 T1 r1  T2 r2 = I alpha
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
Is it possible to find angular acceleration in this way?
 one year ago

shubhamsrgBest ResponseYou've already chosen the best response.2
I am getting confused. @VincentLyon.Fr
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
It seems like there is too much unknown variables.
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
@hartnn @JamesJ @saifoo.khan Can you help me?
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
@zepdrix @AccessDenied
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
Apparently I'm not going to get any help for long time.
 one year ago

rajathsbhatBest ResponseYou've already chosen the best response.0
You don't have to know the direction of rotation of the pulley before you solve the equations. You just take one of the directions as positive and the other one as negative. This choice is completely arbitrary (But since the given problem asks you to take the clockwise direction as positive, you just go ahead with that). After you solve the problem, if the end up with positive angular acceleration, it's in the direction that you chose (In this case, clockwise). If it turns out to be negative, it's in the opposite direction (In this case, counterclockwise).
 one year ago

VincentLyon.FrBest ResponseYou've already chosen the best response.1
Quote : "Clockwise torque = (m2)g(r2) ANti clockwise torque = (m1)g(r1) Greater torque will prevail" This works only if pulley is massless, right? No, this works whatever the moment of inertia of the pulley. It is a good idea to anticipate the direction of motion this way.
 one year ago

geerky42Best ResponseYou've already chosen the best response.1
It makes sense. Thanks, everybody!
 one year ago
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