Players use spin in ball plays like tennis, golf etc. As the ball moves the spin rate will decrease. If the aerodynamic torque : on the ball in flight depends on the forward speed u, density and viscosity of air, the ball diameter D, angular velocity of spin, o and the roughness height e on the ball surface, determine the dimensionless parameters to correlate situation.

Players use spin in ball plays like tennis, golf etc. As the ball moves the spin rate will decrease. If the aerodynamic torque : on the ball in flight depends on the forward speed u, density and viscosity of air, the ball diameter D, angular velocity of spin, o and the roughness height e on the ball surface, determine the dimensionless parameters to correlate situation.

University Physics Volume 1

18th Edition

ISBN:9781938168277

Author:William Moebs, Samuel J. Ling, Jeff Sanny

Publisher:William Moebs, Samuel J. Ling, Jeff Sanny

Chapter11: Angular Momentum

Section: Chapter Questions

Problem 49P: The blades of a wind turbine are 30 m in length and rotate at a maximum rotation rate of 20 rev/min....

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CHECK and THINK Our results give us a way to think about how a person might steer a unicycle. Consider the person, the unicycle, and the Earth as the system. No net torque acts on the system. Ignoring the motion of the Earth, Figure 13.37A shows the initial angular momentum of the system with the unicycle in motion: Li=Ltire. The person leans to his left so that the angular momentum of the tire rotates downward. The total angular momentum must still point to the right (Fig. 13.37B), so the angular momentum of the person must be upward to compensate. The persons angular velocity therefore points upward (parallel to his own angular momentum), and he is able to make a turn. Another way to analyze this situation is to exclude the Earth from the system and calculate the torque done by gravity. This approach is left as a homework problem. FIGURE 13.37 C Reanalyze the unicycles motion in Example 13.15 (page 382). This time, leave the Earth out of the system and explain how the torque exerted by gravity causes the unicycle to turn. Your explanation should involve a diagram.