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Fig. shows an acrobat propelled upward by a trampoline with zero angular momentum. Can the acrobat, by maneuvering his body, manage to land on his back as in Fig. Interestingly, 38% of questioned diving coaches and 34% of a sample of physicists gave the wrong answer. What do you think? (See "Do Springboard Divers Violate Angular Momentum Conservation?", by Cliff Frohlich, American Journal of Physics, July 1979, p. 583, for a full discussion.)

Fig. shows an acrobat propelled upward by a trampoline with zero angular momentum. Can the acrobat, by maneuvering his body, manage to land on his back as in Fig. Interestingly, 38% of questioned diving coaches and 34% of a sample of physicists gave the wrong answer. What do you think? (See "Do Springboard Divers Violate Angular Momentum  Conservation?",  by Cliff Frohlich, American Journal of Physics, July 1979, p. 583, for a full discussion.)

Grade:upto college level

1 Answers

Navjyot Kalra
askIITians Faculty 654 Points
8 years ago
Yes, the acrobat can manage to land on his back and to do so the acrobat just need to bend his body a bit forward such that the center of the gravity of his body gets unaligned from the center of mass. This guarantees a net torque due to gravitational force to act on his body and turn him.
When the acrobat has experienced the turns during his flight he can choose to hit the trampoline again with the position shown below:
232-34_1.PNG
It is important to note that the law of conservation of angular momentum has not been violated here. This is so because, there is an external torque on eth acrobat unlike other cases which will turn the acrobat and by choosing appropriate body position the acrobat can land on the trampoline on his back.

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