Q&A

1. A motion of 1 1/4 vibrations is shown as the following successive motion...
• A-B-C-B-A-B
2. Which part is considered as the amplitude?
• 
  
3. If the same pendulum moves as a-b-c-b-a-b, its motion performs…
• A-B-C-B-A-B-C
4. The number of vibrations performed in every second is…
• The frequency
5. If 120 vibrations happen in one minute, the correct statement is...
• its period is 1/2 seconds
6. A period of a swing is 5 seconds in every minute, the pendulum will perform...
• 12 swings
7. If in 1 over 4 seconds the ruler moves in the B-C-B-A pattern, period of the vibration made by the ruler is…
• 3/4 seconds
8. If the frequency of a vibration is 350 Hz, the period of such a vibration is...
• 1/350 seconds
9. A pendulum performs swings with a frequency 40 Hz. The number of vibrations that it can make within 3 minutes is…
• 7,200
10. If 18,000 waves are performed in 4 minutes, then…
• the period of the wave is 1/75 seconds
11. 1 1.2 wave --> t= 0.5 s What is the frequency of the wave?
• 3 Hz
12. The frequency of a wave is 300 Hz. If the velocity of the wave is 900 m/s, the wavelength is…
• 3 m
13. The length of two transverse waves is 2 m and 2x the wavelength is 3 m.
• The following statements are related to that statement.
• 1. The amplitude of the wave is 4 m.
• 2. The wavelength is 5 m.
• 3. The velocity of the wave is 100 m/s
• If the frequency of the wave is 100 Hz, the correct statement(s) are/is 
• only 3
14. If the vibration direction is perpendicular to the direction of wave propagation, it means that the wave is a...
• transverse wave
15. The velocity of a wave is 150 m/s and its frequency is 300 Hz. The wavelength is...
• 0.5 m
16.  Sound propagates in the air with a speed 600 m/s. If the frequency of the keynote a is 150 Hz, then the wavelength is…
• 4 m

Q&A

1. A spring-mass system vibrates exactly 10 times per second. Find its period and its frequency. 
• f = 10/1 = 10Hz
• T = 1/10 = 0.1
2. A pendulum swings with a period of 0.20 seconds. 
• What is its frequency?
• f = 1/0.20 = 5Hz
• How many times does it pass the lowest point on its path in 1.0 second? in 7.0 seconds? 
• 1 second = 5 times          14 times = 70 times
3. A spring-mass system completes 20.0 vibrations in 5.0 seconds, with a 2.0 cm amplitude. 
• Find its frequency and its period. 
• f = 20/4 = 5Hz
• T = 1/5 = 0.2
• 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? 
4. A pendulum completes 30.0 oscillations per minute. Find its frequency, its period, and its length. 
• f = 30/60 = 0.5Hz
• T = 60/30 = 2s
• A = 2/time = 30
5. A clown is rocking on a rocking chair in the dark. His glowing red nose moves back and forth a distance of 0.42 m exactly 30 times a minute, in a simple harmonic motion. 
• What is the amplitude of this motion? 
• A = 0.42/2 = 0.21m
• What is the period of this motion? 
• 60/30 = 2s
• What is the frequency of this motion? 
• 30/60 = 0.5Hz
• 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 1.00 m apart as the clown rocks. What are the amplitude, period, and frequency of the spot’s motion? 
6. A turning fork has a frequency of 256 Hz. The wavelength of the sound produced by the fork is 1.3 meters. Calculate the velocity of the waves.
• v = wavelength x f           1.3m x 256Hz = 332.8 m/s
7. Green light has a wavelength of 5.2 x 10-7 m and travels through the air at speed of 3 x 108 m/s. Calculate the period and the frequency of this green light waves. 
8. Radio waves travel at the speed of light 3.00  108 m/s. An amateur radio system can receive radio signals at frequencies between 8.00 MHz and 1.20 MHz. What is the range of the wavelengths this system can receive? 

Velocity of a Wave

Velocity

• The rate on how fast a wave propagates
• Formulas


• λ x f *wavelength x frequency*
• λ/t *wavelength / period*

Examples

If a car is moving at 50 km in an hour, what is the velocity?

Answer:

v = 50/60

v = 0.84

If a wave has a frequency of 10 Hz, and its wavelength is 3 cm, what is the velocity?

Answer:

v = λ x f

v = 10 x 3

v = 30 m/s