Exercises 4, 20, 27, 30, and 43 on pages 155-156
Problems 3, 9, and 12 on page 157
1. The density of a rock doesn’t change when it is submerged in water? Does your density change when you are submerged in the water?
A. A human body can be compressed, therefore, volume decreases while mass remains constant. Alternatively, a body will need oxygen in the lungs to survive, so as the water pressure increase with depth, the air pressure in our lungs must be increased to match. This means the mass of the gasses will be increased.
2. The relative densities of water, ice and alcohol are 1.0, 0.9, and 0.8, respectively. Does the ice cubes float higher or lower in a mixed alcoholic drinks? What ...view middle of the document...
The mine air WILL be denser than surface air.
4. Why do you suppose that airplane windows are smaller than bus windows?
A. Because there is a lot more pressure at a higher altitude and a smaller window is stronger.
5. When steadily flowing gas from a larger-diameter pipe to smaller-diameter pipe, what happens to its speed its pressure and the spacing between its streamlines?
A. The speed stays the same because the gas is steadily flowing.
B. The pressure increases because pv=nrt, and the volume of the container decreases so the pressure must increase.
C. The spacing between the streamlines decreases because the same streamlines still exist, but they are crammed closer together to all fit through the smaller pipe.
6. In the deepest part of Lake Superior the water depth is 406 m. Show that the water pressure at this depth is 3978.8 kPa, and the total pressure there is 4080.1 kPa.
A. pressure due to a fluid = rho g h
rho for water = 1000kg/m^3, g=9.8m/s/s and h=406m
P=1000x9.8x406=3.978x10^6PS = 3978kPa
1.01x10^5 Pa = 101kPa
3978kPa + 101kPa = 4079kPa
7. Air in a cylinder is compressed to one-tenth its original volume with no change in temperature. What is the change in its pressure?
A. Pressure increases by 10 times, and 90% of the molecules will escape.
8. In the hydraulic pistons the small piston has a diameter of 2cm and the large piston has a diameter of 6cm. How much more force can the larger piston exert compared with the force applied to the smaller piston?
A. Fs/As = Fb/Ab
Ab = area of bigger piston = pi(6^2) = 36pi
As = area of the smaller piston = pi(2^2) = 4pi
(Fb/Fs) = (Ab/As) = 36pi/4pi
(Fb/Fs) = 9