12. The speed of sound in air is 320 ms-1 and in water it is 1600 ms-1 . It takes 2.5 s for sound to reach a certain distance from the source placed in air.
a. Find the distance.
b. How much time will it take for sound to travel the same distance when the source
is in water?

15. one purpose of the tread pattern on a tire is to a reduce tire wear. b. reduce traction c. allow water to flow away from the tire. d. look impressive.

Air initially at 0.75 bar, 1000 k, and occupying a volume of 0.12 m^3 undergoes two processes. process 1-2: the air is compressed isothermally until the volume is halved. process 2-3: the air undergoes a constant pressure process until the volume is halved again. assume ideal gas behavior. a) determine the mass of the air, in kg. b) the work and the heat transfer for each of the two processes, in kj. (100 kj = 1 bar . m^3)

Which of the following changes will increase the capacitance of a parallel-plate capacitor? (there could be more than one correct choice.) a) increase the charge on the plates b) decrease the poten5al between the plates c) increase the potential between the plates d) introduce a dielectric material between the plates e) decrease the separation between the plates