Use the figure to the right to answer the next problem. A ball of mass of mass m is tied with a light string to a vertical post of radius R p and slides on a frictionless horizontal surface. As the ball travels around the post, the string wraps around the post, shortening the length. At t = 0 s, its speed is v o and radius is r o .

-What is the angular momentum of the ball after the string has wrapped once around the post?
E)cannot be determined

Question

Use the figure to the right to answer the next problem. A ball of mass of mass m is tied with a light string to a vertical post of radius R_p and slides on a frictionless horizontal surface. As the ball travels around the post, the string wraps around the post, shortening the length. At t = 0 s, its speed is v_o and radius is r_o.

Use the figure to the right to answer the next problem. A ball of mass of mass m is tied with a light string to a vertical post of radius R<sub>p</sub> and slides on a frictionless horizontal surface. As the ball travels around the post, the string wraps around the post, shortening the length. At t = 0 s, its speed is v<sub>o</sub> and radius is r<sub>o</sub>. -What is the angular momentum of the ball after the string has wrapped once around the post? A) B) C) D) E) cannot be determined

-What is the angular momentum of the ball after the string has wrapped once around the post?

-What is the angular momentum of the ball after the string has wrapped once around the post?
E)cannot be determined

Quizplus · Accepted Answer

The angular momentum of the ball is conserved as the string wraps around the post, since there is no external torque acting on the system. When the string has wrapped once around the post, the radius of the ball's motion will have decreased to RS1U1B1oS1U1B0/2, and its speed will have increased to 2vS1U1B1oS1U1B0 (conservation of energy). Therefore, the angular momentum of the ball will be:

L = mvr = m(2vS1U1B1oS1U1B0)(RS1U1B1oS1U1B0/2) = mvS1U1B1oS1U1B0RS1U1B1o

which is option C.

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