Mechanical Waves - iPod Physics

Mechanical Waves

Use the following equation v = f to solve for the unknown.

1. V = 300m/s  = 20cm f = 2. V = 300m/s  = 1km f =

3. V = 300m/s  = f = 400Hz 4. V = 1400m/s  = f = 125Hz

4. V =  = 300 m f = 12Hz 5. V = 5m/s  = ¼ m f =

7. V = 150m/s  = f = 5Hz 8. V = 50m/s  = f = 250Hz

Use the following displacement vs time graph to answer questions 1 to 3. The wave speed of this
motion is 10 cm/s.

1. What is the amplitude of the wave?

2. What is the frequency of the wave?

3. What is the wavelength of the wave?
Use the following equation to solve for the unknown.

1. f2 = 880 f1 = 840 v = 340m/s vs = 2. f2 = 780 f1 = 760 v = 340m/s vs =

3. f2 = 1420 f1 = v = 340m/s vs = 20m/s 4. f2 = 650 f1 = v = 340m/s vs = 75m/s

5. f2 = 600 f1 = v = 1420m/s vs = -50m/s 6. f2 = 2 f1 = 3 v = vs = 100m/s

7. f2 = 200 f1 = 210 v = 340m/s vs = 8. f2 = 610 f1 = 710 v = 340m/s vs =

The table below are some possible organ pipe length. Consider the velocity of the wave to be 340
m/s

Left end Right end Frequency Harmonic Length
1 Closed Closed 300 Hz 1st
2 Open Closed 880 Hz
3 Open Open .483 m
4 Closed 440 Hz 3rd 1.20 m
1st 1.55 m
5 Closed Open
2nd 2.00 m

Draw the pipe and the standing waves inside the pipe from the previous problems.
1.

2.

3.

4.

5.

Solve the following word problems.

1. A police car is moving at 29 m/s and is behind a speeding car moving faster in the same direction as the
police car. The radar gun in the police car emits an 8.0x109 Hz electromagnetic wave. The frequency of the
returning wave is measured to be 318Hz less than the emitted frequency. Find the speeder's speed.

2. Question: An ambulance with a siren emitting a whine at 1300 Hz overtakes and passes a cyclist pedaling a
bike at 2.44 m/s. After being passed, the cyclist hears a frequency of 1280 Hz. Use 343 m/s for the speed of
sound in air. How fast is the ambulance moving?

3. A stationary observer hears a frequency of 560 Hz from an approaching car. After the car passes, the
observed frequency is 460 Hz. What is the speed of the car? (speed of sound in air = 343 m/s)

4. A car approaching a stationary observer emits 450 Hz from its horn. If the observer detects a frequency of
470 Hz, how fast is the car moving?

5. While hiking through a canyon, Noah Formula lets out a scream. An echo (reflection of the scream off a
nearby canyon wall) is heard 0.82 seconds after the scream. The speed of the sound wave in air is 342 m/s.
Calculate the distance from Noah to the nearby canyon wall.

6. Mac and Tosh.0 are resting on top of the water near the end of the pool when Mac creates a surface wave.
The wave travels the length of the pool and back in 25 seconds. The pool is 25 meters long. Determine the
speed of the wave.

7. A guitar string with a length of 80.0 cm is plucked. The speed of a wave in the string is 400 m/sec. Calculate
the frequency of the first, second, and third harmonics.

8. A pitch of Middle D (first harmonic = 294 Hz) is sounded out by a vibrating guitar string. The length of the
string is 70.0 cm. Calculate the speed of the standing wave in the guitar string.

9. A frequency of the first harmonic is 587 Hz (pitch of D5) is sounded out by a vibrating guitar string. The
speed of the wave is 600 m/sec. Find the length of the string.