4. a tuning fork is held over a resonance tube, and resonance occurs when the surface of the water is 12 cm below the top of the tube. resonance occurs again when the water is 34 cm below the top of the tube. if the air temperature is 23 ˚c, find the frequency of the tuning fork.

The drag force, fd, imposed by the surrounding air on a vehicle moving with velocity v is given by fd = cdaρv 2/2 where cd is a constant called the drag coefficient, a is the projected frontal area of the vehicle, and ρ is the air density. an automobile is moving at v = 80 kilometers per hour with cd = 0.28, a = 2.3 m2, and ρ = 1.2 kg/m3.