Tag: physics

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Questions Related to physics

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

The sound of lightning flash is heard $3$ second after the flash is seen. The distance of the lightning is $1020$ metre. The speed of sound is:

  1. $1400\ m/s$
  2. $332\ m/s$
  3. $340\ m/s$
  4. $none\ of\ these$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Given data,
Distance $d=1020 m$
Time $t=3s$
Speed$=?$
$Speed=\dfrac{distance }{time}=\dfrac{1020}{3}=340 m/s$

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

The speed of sound in air is  330m/s. It takes 10s for sound to reach a certain distance from the source placed in air. Find the distance.

  1. 669m

  2. 330m

  3. 3300m

  4. 1200m
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$\displaystyle V=330{ m }/{ s },t=2s,V=\frac { d }{ t } $
$\displaystyle d=V\times t$
$\displaystyle =330\times 10=3300m$

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

The smoke from a gun barrel is seen 10s before the explosion is heard. If the speed of sound in air is 340 m/s. Calculate the distance of observer from the gun :

  1. 3400m

  2. 2402m

  3. 62m

  4. 900m
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Speed of sound = 340 m/s
time = 10s
Speed = Distance travelled / time taken
Distance = speed x time
=340 x 10 = 3400 m.

Multiple choice physics propagation of sound waves longitudinal vs transverse wave sound and light comparison of speed of sound with speed of light

On a hot, dry summer day a boy is standing between plane parallel vertical cliffs separated by $75m$. He is $30$m away from one of the cliffs. Consider speed of sound in air on that hot day to be $360m/s$. The boy claps loudly and hearts its successive echoes. The time in seconds at which he hears the first four echoes are respectively

  1. $\displaystyle \frac{1}{6}, \frac{1}{4}, \frac{5}{12}, \frac{5}{12}$
  2. $\displaystyle \frac{1}{6}, \frac{1}{4}, \frac{7}{12}, \frac{2}{3}$
  3. $\displaystyle \frac{1}{4}, \frac{1}{3}, \frac{5}{12}, \frac{5}{12}$
  4. $\displaystyle \frac{1}{6}, \frac{1}{4}, \frac{1}{3}, \frac{5}{12}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

First echo : When sound goes to the cliff 1 and returns to his ear

Distance traveled by sound, $S = 30+30 = 60$ m
Time taken, $t _1 = \dfrac{60}{360} = \dfrac{1}{6}$ s

Second echo : When sound goes to the cliff 2 and returns to his ear
Distance traveled by sound, $S = 45+45 = 90$ m
Time taken, $t _2 = \dfrac{90}{360} = \dfrac{1}{4}$ s

Third echo : When the reflected sound from cliff 1 goes to the cliff 2 and returns to his ear
Distance traveled by sound, $S = 30+75+45 = 150$ m
Time taken, $t _3 = \dfrac{150}{360} = \dfrac{5}{12}$ s

Fourth echo : When the reflected sound from cliff 2 goes to the cliff 1 and returns to his ear
Distance traveled by sound, $S = 45+75+30 = 150$ m
Time taken, $t _4 = \dfrac{150}{360} = \dfrac{5}{12}$ s