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geerky42
 2 years ago
In this system, how can you determine which direction it will rotate?
geerky42
 2 years ago
In this system, how can you determine which direction it will rotate?

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geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1Like, if \(m_1\) is larger than \(m_2\), how can you tell which way it will rotate?

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1Sorry for keeping asking you for help, but can you answer this question, @shubhamsrg ?

shubhamsrg
 2 years ago
Best ResponseYou've already chosen the best response.2Product of mr will decide that

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

shubhamsrg
 2 years ago
Best ResponseYou've already chosen the best response.2Also, am assuming its a massless pulley , right ?

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1Well, 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?

shubhamsrg
 2 years ago
Best ResponseYou've already chosen the best response.2Yes pulleys has mass.

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1The 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)

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1If mass goes upward, T goes first, otherwise, m·g goes first.

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1My 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.

shubhamsrg
 2 years ago
Best ResponseYou've already chosen the best response.2Well simply write eqn of rotation.

geerky42
 2 years ago
Best 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...

geerky42
 2 years ago
Best 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...

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1Any ideas? "Clockwise torque = (m2)g(r2) ANti clockwise torque = (m1)g(r1) Greater torque will prevail" This works only if pulley is massless, right?

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

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1Ugh, I hope I make right guess first, lol.

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1What is angular acceleration is negative? How can I know if my assumption is right or wrong?

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1Problem asks me to "take clockwise direction as positive."

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1Wait, angular acceleration cannot be negative, right?

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

shubhamsrg
 2 years ago
Best ResponseYou've already chosen the best response.2The linear acceleration of both masses will not be equal

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

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1Is it possible to find angular acceleration in this way?

shubhamsrg
 2 years ago
Best ResponseYou've already chosen the best response.2I am getting confused. @VincentLyon.Fr

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1It seems like there is too much unknown variables.

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1@hartnn @JamesJ @saifoo.khan Can you help me?

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1@zepdrix @AccessDenied

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1Apparently I'm not going to get any help for long time.

rajathsbhat
 2 years ago
Best ResponseYou've already chosen the best response.0You 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).

VincentLyon.Fr
 2 years ago
Best ResponseYou've already chosen the best response.1Quote : "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.

geerky42
 2 years ago
Best ResponseYou've already chosen the best response.1It makes sense. Thanks, everybody!
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