Part 4: Angular Momentum 6) What is the angular radians/second? the momentum of

Question

Part 4: Angular Momentum 6) What is the angular radians/second? the momentum of the dynometer in Part 2 when it is rotating at 63.6 784 frmure skater with an initial moment of inertia, 40 kg m2, spins at a rotational speed of 180 rpm. a) What is the skater's rotational speed in radians/second? b) What is the angular momentum of the skater (in SI units)i c) If the skater decreases her rotational inertia to 125 kg·m, what will be the skater's new rotational speed, in radians/second? (Hint: use the principle of conservation of angular momentum.) d) If the skater decreases her rotational inertia to 25 kgm2, what will be the skater's new rotational speed, in rpm?

Explanation / Answer

7.

a)

1 rpm =(2pi/60) rad/sec

W=180*2pi/60 =18.85 rad/sec

b)

angular momentum

L=IW=40*18.85=754 kg-m2/s

c)

By Conservation of angular momentum

Lnew =L

InewWnew =754

Wnew =754/25=30.16 rad/sec

d)

in rpm

Wnew =30.16*(60/2pi)=288 rpm

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