One thing that stringed, wind, and percussion instruments have in common in regard to the sounds they produce is that a. the instruments are struck by tools to produce vibrations and sounds. b. the frequency is always a direct result of adjusting the length of the instrument. c. all of the instruments can be easily adjusted to produce a tone with a certain definite pitch. d. the sound originates from a vibration.

Consider a u-tube whose arms are open to the atmosphere. now equal volumes of water and light oil (ρ = 49.3 lbm/ft3) are poured from different arms. a person blows from the oil side of the u-tube until the contact surface of the two fluids moves to the bottom of the u-tube, and therefore, the liquid levels in the two arms are the same. if the fluid height in each arm is 30 in, determine the gage pressure exerted by the person on the oil by blowing.