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?