A girl sitting on a bar stool with two equal masses in her outstretched arms is

Question

A girl sitting on a bar stool with two equal masses in her outstretched arms is rotating counterclockwise at a speed of . She slowly brings her arms directly towards her body and as a result her angular speed increases.

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A girl sitting on a bar stool with two equal masses in her outstretched arms is rotating counterclockwise at a speed of w. She slowly brings her arms directly towards her body and as a result her angular speed increases Based on this information which statement is true about the moment of inertia I for the system (girl masses)? I decreases I increases I remains constant Submit Answer Tries 0/2 What is the direction of the force applied by her arms? radially outward downwards in the direction of the instantaneous velocity of each mass radially inward upwards Submit Answer Tries 0/2 In the formula for the torque exerted on the masses by the girl (r = rx what is the angle between the force vector F and the position r of the masses? 45 degrees 0 degrees 270 degrees 90 degrees 180 degrees Submit Answer Tries 0/2 The magnitude of the torque on the masses due to the force applied by the girl depends on the angle (e) between the force and position of the masses in the following way: r F cos(0) r F tan(e) r F sin(0) Submit Answer Tries 0/2 Which statement below is true? The angular acceleration of the system results from the torque due to her arms. hee is no net external torque on the system The kinetic energy of the system decreases because the moment of inertia decreases The angular momentum of the system increases Submit Answer Tries 0/2

Explanation / Answer

1) decreases

Because, I = I_girl + I_masses

= I_girl + 2*m*r^2 (here r is the distance from masses to axis of rotationa)

when r decreases total moment of inertic decreases.

2) radially inward.

Because, The masses have acceleration towards the center.

3) 180 degrees

here r and F are in opposite in direction.

4) r*F*sin(theta)

5) There is no not net external torque on the system.

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