1. Briefly explain how an athlete competing in the long jump can prevent the tru

Question

1.     Briefly explain how an athlete competing in the long jump can prevent the trunk from pitching forward after take-off.

2.     True or False: While in the air, Michael Jordan can change the position of his center of gravity relative to the ground by manipulating body segments i.e. Moving mass higher or lower. Explain

3.     Currently, the top male aerialist skiers can perform a triple back somersault with up to five twists before landing. Explain how an elite aerialist can develop twist after leaving the jump (while in the air) and then remove the twist upon completion of their fifth twist.

Explanation / Answer

1) It can be prevented by folding legs in such a way that legs point forward in the direction of flight. Once the person has jumped off, his centre of mass will continue flying like a projectile. However, he can rearrange his body segments in such a way that his legs are further to COM. This will automatically keep the trunk part behind, thus saving him from any injury while landing.

2) FALSE : Once in air, Michael can't apply any net force on his COM and hence can't change the position of his COM. Manipulating the body elements will not help. His COM will continue to fly like a projectile.

3) Right after jump, skiers transform their bodies into a smaller volume and thus reducing their moment of inertia. By the principal of conservation of angular momentum, their rotational speed increases because their rotational inertia has reduced thereby giving them a quick spin. Then they open up their bodies which increases their rotational inertia thereby decreasing the rotational speed which is a must for safe landing.

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