# Help course exercises vol.1 Cap Berkeley. 6 [closed]

1 2. Angular momentum of tetherball. The object of the game tetherball (Fig. 6.24) is to hit the ball hard enough and fast enough to wind its tether cord in one direction about the vertical post to which it is tied before the opposing player can wind it in the opposite direction. The game is exciting, and the dynamics of the ball's motion are complicated. Let us examine a simple type of motion in which the ball moves in a horizontal plane in a spiral of decreasing radius as the cord winds round the post after a single blow that gives the ball an initial speed 1:0 , The length of the cord is I and the radius of the post is a « I. (a) vVhat is the instantaneous center of revolution? (b) Is there a torque about the axis through the center of the post? Is angular momentum conserved? (c) Assume that kinetic energy is conserved and calculate the speed as a function of time. (el) vVhat is the angular velocity after the ball has made five complete revolutions? Ans. w = (l - 1O'7Ta)1:0/[a2 + (l - lO'7Ta?].

-
Hi Emilse, and welcome to Physics Stack Exchange! This is a site for conceptual questions about physics, not general homework help. If you can edit your question to ask about the specific physics concept that is giving you trouble, I'll be happy to reopen it. See our FAQ and homework policy for more information. – David Zaslavsky Jan 8 at 0:19

## closed as too localized by David Zaslavsky♦Jan 8 at 0:19

This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, see the FAQ.