Why is my rotational mechanics homework solution not matching the given choices?

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SUMMARY

The discussion centers on a student's struggle with a rotational mechanics homework problem involving net torque and net force equations. The student incorrectly equated tension force to acceleration, leading to an erroneous calculation of acceleration as 9.2 m/s², which does not match the provided answer choices. Participants emphasized the need to consider the uniformity of tension across the pulley and the necessity of using three equations to solve the problem accurately.

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  • Familiarity with rotational dynamics concepts, including torque and moment of inertia
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Homework Statement


screenshot_47.png


Homework Equations


Net Torque = Moment of Inertia * Angular Acceleration
Net Force = Mass * Acceleration

The Attempt at a Solution


I first applied the first formula on the pulley, I found out that Tension Force = Acceleration
Then, I used Newton's second law on m1 which gave me: 120 - T = 12a ---> 120 - a = 12a ---> 13a =120 ---> a = 9.2

Which is not on the choices,,
any help please
thank you
 
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Sarah00 said:
I first applied the first formula on the pulley, I found out that Tension Force = Acceleration
What did you do here ? How is force of tension equal to acceleration ?

Hint : Is tension on both sides of the pulley the same ? Why / Why not ?
Also , your solution will require three equations .

Hope this helps .
 

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