A boy can swim 75 feet in 12 seconds. What is his rate to the nearest mile per hour?
2 answers:
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Solution:
From Bernoulli equation
ρ
+ ρgh =
ρ
, where ρ is density of water, h – height difference and
and
are the velocities in upper and lower cross sections correspondingly. We take into account that the pressure in both cross-sections is the same and equal to the atmospheric one.
From the continuity and assuming water incompressible:
=
, where
and
are the corresponding cross-sections. As the lower diameter is twice as low as the upper one, we can conclude that
Inserting it back into Bernoulli equations produces:
and the flow rate is