While doing a chin-up, a man lifts his body 0.40 m. (a) How much work must the man do per kilogram of body mass? (b) The muscles involved in doing a chin-up can generate about 70 J of work per kilogram of muscle mass. If the man can just barely do a 0.40-m chin-up, what percentage of his body’s mass do these muscles constitute? (For comparison, the total percentage of muscle in a typical 70-kg man with 14% body fat is about 43%.) (c) Repeat part (b) for the man’s young son, who has arms half as long as his father’s but whose muscles can also generate 70 J of work per kilogram of muscle mass. (d) Adults and children have about the same percentage of muscle in their bodies. Explain why children can commonly do chin-ups more easily than their fathers.
While doing a chin-up, a man lifts his body 0.40 m.
(a) How much work must the man do per kilogram of body mass?
(b) The muscles involved in doing a chin-up can generate about 70 J of work per
kilogram of muscle mass. If the man can just barely do a 0.40-m chin-up, what
percentage of his body’s mass do these muscles constitute? (For comparison, the total
percentage of muscle in a typical 70-kg man with 14% body fat is about 43%.)
(c) Repeat part (b) for the man’s young son, who has arms half as long as his
father’s but whose muscles can also generate 70 J of work per kilogram of muscle mass.
(d) Adults and children have about the same percentage of muscle in their bodies.
Explain why children can commonly do chin-ups more easily than their fathers.
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