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  Exercise 6.11 (waves)

 

1. In an experiment , Lim observes that a simple pendulum completes30 oscillations in

15.0 seconds. What is

(a) the freuenc! of oscillation"  (b) the period of oscillation"

  Answer:  (a) f # 30$15 # % &'

  (b) # 1$f 

  # 1$%

  # 0.5 s

  %.

  alculate the freuenc! of the *iven +ave above.

   Answer : T = 4s

  f =T  

1  Hz 

  = 0.25 Hz 

  3. ased in the displacement-distance *raph of a +ave, find

(a) the amplitude  (b) the +avelen*th of the +ave

  Answer: (a) amplitude = 5 cm

  (b) Waelen!t" = 0.4 cm

5

-5

%  

/isplacement$cm

  ime$s0

/isplacement$cm

  0

/istance$cm

%

5

-5

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. transverse +ave is found to have a distance of cm from a trou*h to a crest, a

freuenc! of 1% &', and a distance of 5 cm from a crest to the nearest trou*h./etermine the amplitude, period, +avelen*th and speed of such a +ave.

 ns+er2

5. *irl moves a lon* slin! sprin* at a freuenc! of 3 &' to produce a transverse+ave +ith a +avelen*th of 0.5 m. What is the +ave speed of the +aves alon* the

slin! sprin*"

  ns+er2

. he fi*ure sho+s a +avefront pattern in a ripple tan produced b! a vibratin*

dipper at freuenc! of 5 &'. What is the +ave speed" 

ns+er2

   f   # 5 &'

  λ  # .0$ # 1.5 cm

  4 # f λ

  # .5 cm s-1

•

6.0 cm

•

4.5 cm

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. he fi*ure sho+s a +avefront pattern in a ripple tan produced b! a vibratin* dipper

at freuenc! of 5 &'. What is the +ave speed"

  Answer:

 f = 5 Hz 

  = #.5 cm s$%

 

6. mechanical stroboscope has 1% slits and rotates at a freuenc! 5 &'. hestroboscope is used to observe +ater +aves. he observer notes there are

successive bri*ht bands at a distance %0 cm. alculate the speed of the +ater +aves.

 

 Answer:  f # n p

  # 1% x 5

# 0 &' 

7. he fi*ure sho+s a loudspeaer produces a sound +ith a freuenc! 300 &'.alculate

(a) the +avelen*th.

(b) the speed of sound

  Answer:(a) 0.& m

(b) ' = f λ 

  = 00 0.5= %50 m s$%

10. *iven +ave travels at a speed of % x 105 ms-1. If the freuenc! of the +ave is 1000&', alculate the +avelen*th

%0 cm (5λ)

λ  # %0$5

  # cm

  4 # f λ

  # 0 x # %0 cm s-1

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  Answer:

  λ = *f 

  = = 200 m 

11. (a) ase on the fi*ure determine,

  (i) the amplitude  (ii) the +ave len*th

  (b) What is the freuenc! of the sound if the speed of sound is 330 ms-1.

  Answer:

  (a) (i) 2 cm

8ichael carried out an experiment to determine the period and freuenc! of a

loaded sprin*. &e found that the sprin* made %5 complete oscillations in 10 seconds.

(a) What is the

(i) period and

(ii) freuenc! of the sprin* oscillations"

(b) 8ichael observed that the amplitude of the oscillations decreased +ith time.

(i) 9ive one reasons for the phenomenon.(ii) :etch a displacement-time *raph for this phenomenon.

(c) fter this, 8ichael immersed the sprin* in a container filled +ith +ater.&e observed that the amplitude decreased at a faster rate. ;xplain +h!.