Day 12, Physics 131

HW Problem 14-4

• A tsunami traveling across deep water can have a speed of 750 km/hr and a wavelength of 310 km.

• ? What is the frequency of such a wave ?

HW Problem 14-14

• A brother and sister try to communicate with a string tied between two tin cans.

• Given: the string is 9.5 m long, has a mass of 32 g, and is pulled taut with a tension of 8.6 N.

• ? How much times does it take for a wave to travel from one end of the string to the other ?

HW Problem 14-30

• When you drop a rock into a well, you hear the splash 1.5 seconds later.

• ? (a) How deep is the well ?• ? (b) If the depth of the well were doubled,

would the time required to hear the splash be greater than, less than, or equal to 3.0 s ? Explain ??

HW Problem 14-3

• In a pig-calling contest, a caller produces a sound with an intensity level of 110 dB.

• ? How many callers would be required to reach the pain level of 120 dB ? Prove it!

HW Problem 14-50

• You hear the siren of an approaching fire truck, so you pull over and stop. As the truck approaches, you hear a tone of 460 Hz; as the truck recedes, you hear a tone of 410 Hz.

• ? How long will it take for the truck to get from your position to the fire 5.0 km away, assuming it maintains a constant speed ?

HW Problem 14-61

• A pair of in-phase stereo speakers is placed side by side, 0.85 m apart. You stand directly in front of one of the speakers, 1.1 m from the speaker.

• ? What is the lowest frequency that will produce constructive interference at your location ?

HW Problem 14-72

• A guitar string 66 cm long vibrates with a standing wave that has three antinodes.

• ? (a) which harmonic is this ?• ? (b) What is the wavelength of this wave ?

HW Problem 4-80

• Two tuning forks have frequencies of 278 Hz and 292 Hz.

• ? What is the beat frequency if both tuning forks are sounded simultaneously ?