# lec10 - L ECTURE 10 E NERGY IN A THLETES • Information on...

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Unformatted text preview: L ECTURE 10: E NERGY IN A THLETES • Information on grades • Energy conservation in the human body • Power • Metabolism • Heat dissipation 1. Which of these is not a form of energy? (a) Work ~ F · ~ d (b) Gravitational potential energy mgh (c) Kinetic energy 1 2 mv 2 (d) Thermal motion of atoms and molecules (e) They are all forms of energy 2. Which statement about “conservation of energy” is false ? (a) Energy changes from one form to another but is never lost. (b) A pitcher does work on a baseball that appears as kinetic energy. (c) When a snowboarder in the halfpipe is at the top of his jump he has converted his potential energy into kinetic energy. (d) When you rub your hands together you do work against friction and the energy is “lost” to thermal energy. (e) To clear the bar, pole vaulters convert kinetic energy and elastic potential energy into gravitational potential energy. The Three Laws of Thermodynamics The First Law Energy is conserved. “You can’t .” The Second Law The total entropy (a measure of disorder) always increases. “You can only .” The Third Law Absolute zero of temperature. “You can’t .” The Second Law of Thermodynamics & Sports • The 2nd law involves the relationship between macroscopic and microscopic forms of energy. • Thermal energy is difficult to convert to useful work. There are always some losses to thermal energy. • For example, in running, only ∼ 25% of the burned calories are converted into useful mechanical work. • Work done against friction and fluid resistance-→ heat • Work done against gravity and elastic forces-→ potential energy Energy conservation for the human body Internal E nergy C hemical E nergy Mechanical Work Heat E nergy Energy conservation for the human body...
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lec10 - L ECTURE 10 E NERGY IN A THLETES • Information on...

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