Vibration and waves

Question and answer
http://classjump.com/s/sidiq/documents/Worksheet4VibrationWaves.pdf?

With different values 
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1. A spring-mass system vibrates exactly 9 times per second. Find its period and its 
frequency

1A) 

Period = T= 1/9 seconds

Frequency = n/t = 9/1 = 9Hz
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2.A pendulum swings with a period of 1 second.

a. What is its frequency?

2aA) 1/T = 1/1 = 1Hz
b. How many times does it pass the lowest point on its path in 2.0 second? in 79.0 seconds?

2bA) 2times, 79times. Since its 1Hz
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3. A spring-mass system completes 30.0 vibrations in 5.0 seconds, with a 2.0 cm amplitude.

a. Find its frequency and its period.

3aA)

Frequency : 6Hz
Period : 1/6 seconds

b. The same mass is pulled 5.0 cm away from the equilibrium position, then released. What 
will the period, the frequency, and the amplitude be?

3bA)

Frequency = 6Hz
Amplitude = 5cm
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4. A pendulum completes 40.0 oscillations per minute. Find its frequency, its period, and its 
length.

4A) 
Frequency = 40/60 = 2/3 Hz 
Period = 1/0.6 = 1.667
Length = Unknown
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5. A clown is rocking on a rocking chair in the dark. His glowing red nose moves back and forth 
a distance of 5m exactly 30 times a minute, in a simple harmonic motion.
a. What is the amplitude of this motion?

5/2 = 2.5

b. What is the period of this motion?

T= 1/2.5 = 0.4 Seconds

c. What is the frequency of this motion?

30/60s = 1/2 Hz

d. The top of the clown’s hat contains a small light bulb that shines a narrow light beam. The 
beam makes a spot on the wall that goes back and forth between two dots placed 10.00 m 
apart as the clown rocks. What are the amplitude, period, and frequency of the spot’s 
motion?

Amplitude = 10m / 2 = 5m

Period = 0.4 Seconds (same as 5.b)

Frequency = 1/2Hz (same as 5.c)

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6. A turning fork has a frequency of 256 Hz. The wavelength of the sound produced by the 
fork is 46 meters. Calculate the velocity of the waves

Velocity λ x F
= 46m x 256 Hz
=11776 m/s
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7. Green light has a wavelength of 5.4 x 10-7m and travels through the air at speed of 3 x 108 m/s. 
Calculate the period and the frequency of this green light waves.

Period = 1/F = 0.556x 1015

Frequency = v/λ = 3/5.4 x 108 / 10-7 = 0.556 x 1015
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8. Radio waves travel at the speed of light (3.00 x 108 m/s). An amateur radio system can 
receive radio signals at frequencies between 12.00 MHz and 1.20 MHz. What is the range of 
the wavelengths this system can receive?

F = 12MHz & 1.2MHz

λ1 = 3x108 / 8 = 3/8 x 108 = 0.375 x 108 Metres

λ2 = V/F2 = 3x108 / 1.2 = 2.5 x 108 Metres

 V= λ x F
λ = V / F