Mind Map of Vibrations and Waves

Click for a preview of the mind map

Exercise on Chapter 18

14. If 20,000 waves are performed in 2 minutes, then the period is . . .

Answer:
F = 20,000  = 166.7 Hz
         120
P =    1    s
      166.7

15. Look at the following figure of a wave.
                                                                      t = 10 s                      
                                                 |                                                      |

The frequency of the wave is . . .

Answer:

F =   1   = 0.1 Hz

       10

16. The frequency of a wave is 200 Hz. If the velocity of the wave is 400 m/s, the wavelength is . . .

Answer:

Wavelength = velocity  = 400  = 2 m 

                      frequency   200

17. Look at the following figure of a transverse wave.

With the frequency of 50 Hz and wavelength of 1 m, the velocity of the wave is . . .

Velocity = wavelength x frequency

               = 1 x 50 = 50 m/s

18. If one complete wave consists of one compression and one expansion part, then the name of the wave is . . .

Answer: Longitudinal wave

19. The velocity of a wave is 100 m/s and its frequency is 150 Hz. The wavelength is . . .

Answer:

wavelength = velocity   = 100  = 0.67 m

                      frequency   150

20. Sound propagates in the air with a speed 350 m/s. If the frequency of the keynote a is 450 Hz, then the wavelength is . . .

Answer:

wavelength = velocity  = 350 = 0.78 m

                      frequency  450 

Vibration and Waves Worksheet

1. Known that a spring-mass system has
Vibration  = 20 times/s
Frequency= ?
                 = n  = 20 = 20 Hz
                     t       1
Period       = ?
                 = 1  = 1 seconds = 0.05 seconds
                     f    20

2. Known that a period of a pendulum is 0.40 seconds
a) Find the frequency
Frequency= 1  =   1     = 2.5 Hz
                    T     0.40
b) Times passing the lowest point in 1 second
= 2.5 times = 5 times (1 vibration will touch the lowest point 2 times)
c) Times passing lowest point in 7 seconds
= 5 x 7 = 35 times

3. Known that...
- 10 vibrations in 6 seconds
- amplitude = 4 cm
a) Find the frequency and period
F = n  = 10  = 1.67 Hz
       t       6
P = 1  =   1   = 0.15 s
       f     1.67
b) The amplitude is 4 cm. Find the period and frequency.
- Same answers as in 3(a) -

4. Known that there are 25 oscillations/50s. Find the frequency and period.
F = n  = 25  = 0.5 Hz
       t      50
P = 1  = 1   = 2 seconds
       f     0.5

5. Known that the distance is 0.40 m and the object vibrates 25 times/min.
a) Find the amplitude
= 0.40 m  = 0.2 m
       2
b) Find the frequency
= n  = 25  = 0.417 Hz
    t      60
c) Find the period
= 1  =     1     = 2.4 s
    f      0.417
d) Find the amplitude if it is 2 meters
= 2 m  = 1 m
     2

6. Known that the frequency of an object is 260 Hz and the wavelength is 1.5 m. Find the velocity of that object.
= wavelength x frequency = 1.5 m x 260 Hz = 390 m/s

                                                                                   -8                                                    9
7. Known that the wavelength of an object is 6 x 10  m and the speed is 4 x 10  m/s
Find the period and frequency.       9                         17
Frequency =   velocity    =  4   x 10  = 0.67 x 10
                     wavelength    6       10-8
Period =  1  =      1         17 = 1.5 seconds
                f       0.67 x 10
                                                                       
8. Known that the velocity of an object is 12 m/s and the frequency is 2 Hz. Find the wavelength.
velocity = wavelength x frequency
wavelength=   velocity    = 12  = 6 m
                      frequency       2

Velocity of Wave

A wave has a velocity when a vibrating object is not moving or propagating from one place to another. The velocity of a wave defines how fast a wave propagates.

The two formulas of velocity are as follows:

1. v =      λ (wavelength)             /     s (distance to be covered)

           t (period of the wave)                   t (covering time)

2. v =  λ (wavelength) x f (frequency)

Questions including answers of the two formulas:

2nd Formula

  The velocity of a wave is 50 m/s. If the wavelength is 10 m, what is the frequency of that wave?

v = λf  so  f =  v 

                        λ

f =  50 m/s  = 5 Hz

       10 m

1st Formula

  Given: distance to be covered = 6λ

              time needed = 4 s

  Find:   velocity

v =  6  = 1.5 m/s

       4

Wave Properties

- A wave is a disturbance or vibration which propagates along a
medium. An example is the waves on a water surface.


- Mechanical wave is a wave that needs a medium in which the wave propagates. An example is waves in a rope, because they need media for their propagation.


- Electromagnetic wave is a wave that does not need any media to propagate. Such examples are signal of a cell-phone.


- Transverse wave is an element of a wave that is always in the form of a peak and valley. One complete wave has one peak and one valley. It is either on the rope, on water, or on slinky (long, flat spring made of steel).

- Longitdinal wave does not have peaks and valleys unlike transverse wave, instead, it has compression and expansion part. A complete wave has one compression and one expansion part. An example is vibration in gases.

- A wave length is the length of a wave consists of one peak and one valley.


http://www.dptips-central.com/light.html
http://wiki.answers.com/Q/What_are_the_example_of_longitudinal_waves
2B Science Book