Merry-go-round at rest, inertia, kid running on it problem.

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SUMMARY

The problem involves a 45 kg child running at 3.50 m/s tangentially to a stationary merry-go-round with a moment of inertia of 555 kg m² and a radius of 2.45 m. Upon the child jumping off, the system begins to rotate, necessitating the use of conservation of angular momentum to determine the angular speed. The initial misunderstanding regarding acceleration and torque was clarified, emphasizing that the solution relies on angular momentum principles rather than linear dynamics.

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1barcafan
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Homework Statement


a 45kg child runs with a speed of 3.50m/s tangential to the rim of a stationary merry-go-round that has a momentum of inertia of 555 kg m^2, and a radius of 2.45m. when the child jumps off, the entire system begins to rotate. what is the angular speed of the system?



Homework Equations





The Attempt at a Solution


i found the circumference of the merry-go-round. assuming initial displacement is 0, final is 15.39 (circumfrence), initial velocity is 3.50m/s, and final velocity is 0, i found time to be 8.79s and acceleration to be -.40 m/s^2. using that acceleration and the mass of the child i found force, then using that force and distance i found torque. (i wasn't even taught torque, i just watched a youtube video on it and it seemed appropriate to incorporate it into this problem). once i did all of this, i just got stuck, I've never had a problem that asked for angular speed before so this is just something completely foreign.
 
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Hi 1barcafan! :smile:
1barcafan said:
a 45kg child runs with a speed of 3.50m/s tangential to the rim of a stationary merry-go-round that has a momentum of inertia of 555 kg m^2, and a radius of 2.45m. when the child jumps off, the entire system begins to rotate. what is the angular speed of the system?

I don't understand the question. :confused:

Are you sure it doesn't say that the when the child jumps onto the merry-go-round, the entire system (ie merry-go-round plus child) begins to rotate?

Anyway, this has nothing to do with acceleration (or torque ).

This is a collision, so use conservation of angular momentum. :wink:
 

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