Download Fluid Practice Problems(9/27)

Fluid Practice Problems
Buoyant Force
1. A piece of metal weighs 50.0N in air, 36.0N in water, and 41.0Nin an unknown
liquid. Find the densities of the following:
a. The metal
b. The unknown liquid
2. A 2.0kg rectangular air mattress is 2.00m long, 0.500m wide, and 0.100m thick.
What mass can it support in water before sinking?
Pressure
3. A person rides a lift to a mountaintop, but the person’s ears fail to “pop”- that is,
the pressure of the inner ear does not equalize with the outside atmosphere.
The radius of each eardrum is 0.40cm. The pressure of the atmosphere drops
from 1.010X105 Pa at the bottom of the lift to 0.998X105Pa at the top.
a. What is the pressure difference between the inner and outer ear at the top
of the mountain?
b. What is the net force on each eardrum?
4. Water is to be pumped to the top of the empire state building, which is 366m
high. What gauge pressure is needed in the water line at the base of the building
to raise the water to this height? (the density of water is 1.00X10 3kg/m3)
Equation of Continuity
5. The aorta carries blood away from the heart at a speed of about 40cm/s and has
a radius of approximately 1.1cm. The aorta branches eventually into a large
number to tiny capillaries that distribute the blood to the various body organs. In
a capillary, the blood speed is approximately 0.07 cm/s, and the radius is about
6.0X10-4cm. Treat the blood as an incompressible fluid and determine the
approximate number of capillaries in the human body.
Bernouilli Equation
6. Prairie dogs are burrowing rodents. They do not suffocate in their burrows
because the effect of air speed on pressure creates sufficient air circulation. The
animals maintain a difference in the shapes of two entrances to the burrow, and
because of this difference, the air (Rho=1.29kg/m3) blows past the openings at
different speeds, as the drawing indicates. Assuming that the openings are at
the same vertical level, find the difference in air pressure between the openings
and indicate which way the air circulates.
Va=8.5m/s
Vb=1.1m/s