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A merry-go-round has a radius of 2.6 m and a moment of inertia 857 kg · m2. A boy of mass 44 kg runs tangent to the rim at a speed of 5.0 m/s and jumps on. If the merry-go-round is initially at rest, what is the angular velocity (in rad/s) after the boy jumps on? (Enter the magnitude.)

Respuesta :

To give an appropriate solution to this problem we require the concepts of Angular Moment and Inertia Moment,

The angular velocity is given by,

[tex]\omega_f = \frac{L}{I}[/tex]

Where,

L is the initial angular momentum, equal to

[tex]L =mvr[/tex]

And I the moment of inertia, which for a point rotating in a circle is given by

[tex]I=mr^2[/tex]

Here m is the mass and r the radius.

For our problem the values are,

[tex]m= 44kg\\v=5m/s \\r=2.6m[/tex]

Then the angular momentum is

[tex]L = mvr = (44)(5)(2.6)\\L = 576kgm^2/s[/tex]

In the other hand the moment of inertia of the system is,

[tex]I=I_0 +mr^2\\I = 857+(50)(2.6)^2\\I = 987kgm^2/s[/tex]

Finally we can calculate the angular momentum, which is given by,

[tex]\omega_f=\frac{L}{I}= \frac{576}{987}\\\omega _f= 0.584rad/s[/tex]

Therefore the angular velocity after the boy jumps on is 0.584rad/s