Stuck on a Torque Problem Help is appreciated

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Homework Help Overview

The discussion revolves around a torque problem involving a mass attached to a spool. The problem includes parameters such as mass, radius, moment of inertia, and the distance the mass falls, with the goal of determining the time it takes to reach the floor.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply the relationship between torque and angular acceleration but expresses confusion regarding the calculation of angular acceleration and the need for additional values such as acceleration. Some participants suggest using the SUVAT equations and emphasize the relationship between downward acceleration and rotational acceleration.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem. Some guidance has been offered regarding the assumptions needed to analyze the forces and accelerations involved, but there is no explicit consensus on the next steps or methods to be used.

Contextual Notes

Participants are navigating the complexities of relating linear and rotational motion, with some uncertainty about the necessary values and relationships to apply in the calculations. The original poster's calculation of the spool's mass appears to be a point of confusion.

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Stuck on a Torque Problem! Help is appreciated!

1. A mass of 45.5kg is attached to a light string (negligible) that is wrapped around a cylindrical spool of radius 10cm and moment of inertia 4.0kg*m^2. The spool is suspended from the ceiling, and the mass is then released from rest a distance 3.5m above the floor. How long does it take to reach the floor?
2. Sum of the torques = Inertia * angular acceleration
3. I calculated the mass of the spool to be 400kg by using I=mr^2. After that, I'm directionless! Thanks in advance for your help :)
 
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Distance is given and you are required to find time.
You can use SUVAT equation to find the time.
Another value you need to find is the accceleration.
Downward acceleration of the mass is also related to rotational acceleration of the spool.
 


that helps a bit but I'm still confused on how to calculate angular acceleration since i don't know ω...
 


cngest said:
that helps a bit but I'm still confused on how to calculate angular acceleration since i don't know ω...

You have find α not ω.
Just assume downward acceleration equal to a.
Then draw a fbd of the mass.

Assume a force is pulling 2 bodies connected by a string. But here the second body is a spool.
 
Last edited:

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