Tag: physics

Questions Related to physics

What is the change in frequency observed by a stationary observer when a source of frequency f; Take speed of sound in $air=V _0$

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

  1. $\frac{V _0}{V _0+V _s}f$

  2. $\frac{V _0V _s}{V _0+V _s}f$

  3. $\frac{2V _0V _s}{V _0^2-V _s^2}f$

  4. $\frac{2V _s}{V _0^2-V _s^2}f$

Show answer
Correct Option: B

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:

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

  1. $1400\ m/s$

  2. $332\ m/s$

  3. $340\ m/s$

  4. $none\ of\ these$

Show answer
Correct Option: C
Explanation:

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

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.

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

  1. 669m

  2. 330m

  3. 3300m

  4. 1200m

Show answer
Correct Option: C
Explanation:

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

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 :

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

  1. 3400m

  2. 2402m

  3. 62m

  4. 900m

Show answer
Correct Option: A
Explanation:

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

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

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

  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. $\displaystyle \frac{1}{6}, \frac{1}{4}, \frac{1}{3}, \frac{5}{12}$

Show answer
Correct Option: A
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

The mass of 0.5 litre of hydrogen gas at NTP will be approximately

physics learning how to measure measurement of area and volume measurement of volume measurement of area, volume and density

  1. 0.0892 g

  2. 0.045 g

  3. 2 g

  4. 22.4 g

Show answer
Correct Option: B
Explanation:

$PV=mRT$

Under NTP 
 $P=10^5N/m,\ V=0.5L=0.5\times10^{-3},\ T=298K,\ R=8300/2$

$\Rightarrow 10^5\times 0.5\times 10^{-2}=m\times 8300\times 298/2$
$\Rightarrow m=0.042\ g$

The space occupied by the object is called ....................... .

physics learning how to measure measurement of area and volume measurement of volume measurement of area, volume and density

  1. Area

  2. Mass

  3. density

  4. Volume

Show answer
Correct Option: D
Explanation:

Volume of the object is defined as the space occupied by the object.

Mass per unit volume is ....................... .

physics learning how to measure measurement of area and volume measurement of volume measurement of area, volume and density

  1. Density

  2. Mass

  3. Volume

  4. All of the above

Show answer
Correct Option: A
Explanation:
Density of object is defined as the mass of the body per unit is volume.
$Density = \dfrac{Mass}{Volume}$

Express $1  ml $ in $m^3$.

physics learning how to measure measurement of area and volume measurement of volume measurement of area, volume and density

  1. $10^{-3}$

  2. $10^{-6}$

  3. $10^{-9}$

  4. None of the above

Show answer
Correct Option: B
Explanation:

$1ml=10^{-3}L=10^{-3}\times10^{-3}m^3=10^{-6}m^3$

1 liter = ______cm$^3$

physics learning how to measure measurement of area and volume measurement of volume measurement of area, volume and density

  1. 100

  2. 1000

  3. 10

  4. 1

Show answer
Correct Option: B
Explanation:

We know that: $1 m^3=1000\ liter$

Aslo, $1m^3=10^6cm^3$
$1000\ liter=10^6 cm^3$
$1\ liter=1000\ cm^3$