Practice Problems Angular Momentum
Directions: On this worksheet you will practice using the basic formulas and relationships for angular momentum.

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Question 1  A 27-gram point mass is traveling at a velocity of v = 2.3 m/sec parallel to the x-axis along the line y = 0.3 meters. What is its angular momentum with respect to the origin?

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Question 2  A whirligig, mounted on the top of a stake, is composed of metal biplane with a large spinning propellor. Initially the propellor has an angular momentum of 0.731 kg m2/sec. Later a blustery wind blowing for 2.3 seconds increases the propellor's angular momentum to 1.975 kg m2/sec. What average torque did the wind provide to the propellor?

image courtesy of Wind & Weather
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Question 3  One child, sitting on a tilt-n-spin with her arms held straight out at shoulder level, is pushed by second child. When the pushing stops, her initial rate of spin is 1.8 rad/sec. When she both brings her arms in so she can grasp the edge of the top wheel and also bends her head and shoulders over her crossed legs her rate of spin increases to 3.88 rad/sec. Find the ratio of the child's final moment of inertia to her initial moment of inertia.

image courtesy of Fun and Function
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Question 4  A turntable with a moment of inertia of 6.76 x 10-3 kg m2/sec is initially turning at 331/3 rpm while it is playing the first record. A second record is stacked on the spindle and is ready to be dropped when the first LP finishes and the arm retracts. The second record has no initial rotation - it is at rest.The second record has a mass of 122 grams and a diameter of 30 cm. If you treat the second LP as a cylinder, what will be the instantaneous rotation rate of the turntable with both records when the second record lands on the first record? NOTE: this effect was actually noticeable as the turntable took a few milliseconds to get back up to speed after the second record was dropped on the top of the first record.