As you read this problem, your brain is consuming about 23.3 W of power. a) How

Question

As you read this problem, your brain is consuming about 23.3 W of power.

a) How many steps with a height of 19.9 cm must a person of mass 74 kg climb to expend a mechanical energy equivalent to one hour of brain operation?


A typical human brain, which is 77% water, has a mass of 1.4 kg. Assuming that the 23.3 W of brain power is converted to heat, what temperature rise would you estimate for the brain in one hour of operation? Ignore the significant heat transfer that occurs between a human head and its surroundings, as well as the 23% of the brain that is not water.

Explanation / Answer

Energy required for 1 hour operation = 23.3*3600 = 83880 J
Height to be climbed is
74*9.8*h = 83880
h = 115.66 m
No. of steps = 115.66/0.199
= 581 steps

mass of water = 0.77*1.4 = 1.078 kg

83880 = 1.078*4186*t

t = 18.59 K = 18.59 degrees centigrade

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