Real Question This Time about a Merry go Round

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Homework Help Overview

The discussion revolves around a physics problem involving a disk-shaped merry-go-round, focusing on angular momentum and the effects of a person jumping onto it. The problem includes parameters such as the radius, mass of the merry-go-round, and the speed of the person.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the relevance of kinetic energy versus angular momentum in solving the problem. There are attempts to set up equations involving angular momentum and moments of inertia, with some questioning the correctness of their formulations.

Discussion Status

Some participants have provided equations and attempted calculations, while others have pointed out potential issues with units and assumptions. There is an ongoing exploration of the correct approach to the problem, with no clear consensus yet.

Contextual Notes

Participants are navigating the transition from linear to angular quantities and are addressing the need for consistent units in their calculations. There is an emphasis on ensuring that angular speed is expressed in radians per second.

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A disk-shaped merry-go-round of radius 2.74 m and mass 168 kg rotates freely with an angular speed of 0.737 rev/s. A 51.7 kg person running tangential to the rim of the merry-go-round at 2.86 m/s jumps onto its rim and holds on. Before jumping on the merry-go-round, the person was moving in the same direction as the merry-go-round's rim. What is the final angular speed of the merry-go-round?
 
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Actually, ignore all of this...the kinetic energy is not relevant...i need to focus on angular momentum

therefore the equation should be:
rmv(child) + Iw = (i + mr^2)(w)

is this correct?
 
So, when I tried to solve this i got:

(2.74)(51.7)(2.86) + (1/2(168(2.74^2)(0.737) = [(.5(168)(2.74^2) + (51.7 x 2.74^2)] w

then i solved for w and got 0.8539 which is not correct

what am i missing?
 
In order for Iw to equal angular momentum, w must be given in standard units of radians/sec (not rev/sec).
 

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