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

Waves

Definition

A wave is a vibration that travels through a distance which increases along a medium.

Types of Wave

• Mechanical Wave

• A wave that needs a medium in order to propagate is known as a mechanical wave.
• Example: Ocean wave

• Electromagnetic Wave
• An electromagnetic wave is a wave that does not need a medium or any media to propagate.
• Example: Microwave radiation

Elements of a Wave

• Transverse Wave
• A transverse wave is always in the form of a peak.
• Longitudinal Wave
• A longitudinal wave consist of a compression-expansion pattern throughout the wave.

Wavelength

• The distance of one wave

Frequency, Period and Amplitude

Frequency

The number of vibrations an object executes in one second is known as frequency. Hertz (Hz) is used as the unit of measurement for this phenomenon. The formula to this scientific meaning is F = n/t. *n = vibration , t = time*

Example

If a pendulum performs 360 swings in 2 minutes, what is the frequency?
Answer:
F = n/t
F = 360/120
F = 3 Hz




Period
The time it takes an object to accomplish one vibration is called period. The formula to find the period is T = t/n or T = 1/f. *t = time , n = vibration*

Example
What is the period if an object performs 60 vibrations in 30 seconds?
Answer:
T = t/n
T = 30/60
T = 0.5 seconds

Amplitude
The amplitude of an object is the farthest position from its balance position. Therefore, the formula to calculate amplitude is A = d/f. *d = distance , f = frequency*

Vibration

What is vibration?
The continuous back and forth movement in which an object imitates is known as vibration.

Examples

• A running motor

• The strumming of guitar strings        
• A car traveling over a rough path
• A pendulum

Pendulum as an Example

• 1

• 1 1/2

• 2

• 2 1/4

• 2 3/4

Conservation of Mechanical Energy

Mechanical Energy
The energy that is associated with motion is known as mechanical energy. There are two forms of mechanical energy, otherwise known as kinetic and potential energy.

Examples:

• A flying aircraft
• A moving vehicle

Kinetic Energy
Kinetic Energy occurs when the object is in motion.

Examples:

• A moving bicycle

Potential Energy
Potential Energy occurs when the object is not in communication with the ground. 

Examples:

• A flying kite
• A hanging swing

Formulas

• Kinetic Energy
• 1/2 x V2
• Potential Energy
• m x g x h

Conservation of Energy
Energy that can't be made or destroyed but can only be transformed is known as conservation of energy.