Chapter 12, 13: Ideal Gas & Fluids
ρ  m/V
Example Questions & Problems
p  F/A
 v1A1  v 2 A 2
pV  nRT
pgauge  p  1 atm
p1  21  v12   gy1  p2  21  v 22   gy 2
Example 12.1
When you stifle a sneeze, you can damage delicate tissues because the pressure of the air that
is not alowed to escape may rise by up to 45 kPa. If this extra pressure acts on the inside of
your 8.4-mm-diameter eardrum, what is the outward force?
Example 12.2
a. What isthe absolute pressure of the air in your car's tires, in psi, when your pressure gauge
indicates they are inflated to 35.0 psi? Assume you are at sea level.
b. Suppose you inflate your car tires to 35 psi on a 20oC day. Later, the temperature drops to
0oC. What is the pressure in your tires now?
Example 13.1
A research submarine has a 20-cm-diameter window 8.0 cm thick. The manufacturer says the
window can withstand forces up to 1.0 × 106 N. What is the submarine's maximum safe depth in
seawater? The pressure inside the submarine is maintained at 1.0 atm.
Example 13.2
A U-shaped tube, open to the air on both ends, contains mercury. Water is poured into the left
arm until the water column is 10.0 cm deep. How far upward from its initial position does the
mercury in the right arm rise?
Example 13.3
A 10 cm wood block with a density of 700 kg/m3 floats in water.
a. What is the distance from the top of the block to the water if the water is fresh?
b. If it's seawater?
Example 13.4
The 3.0-cm-diameter water line splits into two 1.0-cm-diameter
pipes. All pipes are circular and at the same elevation. At point A,
the water speed is 2.0 m/s and the gauge pressure is 50 kPa.
What is the gauge pressure at point B?