A bowling ball is suspended from the ceiling of the lecture hall, becoming the bob of a large pendulum. The lecturer takes the bowling ball and moves back until the arc of the ball\\\'s swing is at the level of his nose. He then marks the spot. If he then lets the ball go, when it swings back it will just touch the tip of his nose. Remaining motionless when the ball swings back toward you is difficult because the heavy bowling ball is moving pretty fast at the bottom of its swing, and you knew that it\\\'s headed directly for your nose. But, as energy is conserved, the ball can\\\'t possibly rise higher than its original height. The gravitational potential energy put into the ball by raising it to the height of your nose is converted into kinetic energy of motion at the bottom of its swing. Of course, the taller the lecturer the faster the ball travels at the bottom of its swing. Make certain that the ball isn\\\'t pushed when released.

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