Tag: physics

Questions Related to physics

Box $1$ and box $2$ are identical when at rest relative to each other. An astronaut floating in intergalactic space sees the two boxes fly by from the astronaut's left to his right. Box $1$ flies by at $(0.8)c(80$% of the speed of light), and box $2$ flies by at $(0.9)c(90$% of the speed of light).
Because of relativistic effects, what is true from the point of view of the astronaut?

lorentz transformation and muon experiment option a: relativity physics

  1. Box $2$ is longer and taller than box $1$

  2. Box $2$ is longer and not as tall asbox $1$

  3. Box $1$ is longer and taller than box $2$

  4. Box $1$ is longer and not as tall as box $2$

  5. Box $2$ is shorter and the same height as box $1$

Show answer
Correct Option: E
Explanation:
According to relativity, the ;ength of moving object parallel to the direction of motion gets shortened but the length perpendicular to the motion remains the same.
Let the rest length (parallel to the motion) and rest height of both the boxes be $L _o$ and $h _o$ respectively.
Box 1 :     $v = 0.8c$
$\therefore$ Length of box 1 observed by the astronaut        $L' _1 = L _o \sqrt{1- v^2/c^2} = L _o \sqrt{1- (0.8)^2}  =0.6L _o$

Box 2 :     $v = 0.9c$
$\therefore$ Length of box 2 observed by the astronaut        $L' _2 = L _o \sqrt{1- v^2/c^2} = L _o \sqrt{1- (0.9)^2}  =0.44L _o$

$\implies$    $L _1' > L _2'$    and  $h' _1 = h' _2 = h _o$
Hence option E is correct.

A resonance tube is resonated with tuning fork of frequency 256 Hz. If the length of first and second resonating air columns are 32 cm and 100 cm, then end correction will be 

resonance oscillations physics

  1. $1 cm$

  2. $2 cm$

  3. $4 cm$

  4. $6 cm$

Show answer
Correct Option: B

If $\omega _{0}$ is natural frequency of damped forced oscillation and $p$ that of driving force, then for amplitude resonance

resonance oscillations physics

  1. $p _{r}= \omega _{0}$

  2. $p _{r}< \omega _{0}$

  3. $p _{r}> \omega _{0}$

  4. $p _{r}> = \omega _{0}$

Show answer
Correct Option: A

Which of the following is an example of mechanical resonance?

resonance oscillations physics

  1. A child on a swing.

  2. A pendulum.

  3. A tuning fork.

  4. Nuclear magnetic resonance

Show answer
Correct Option: A,B
Explanation:

$Answer:-$ A,B

Mechanical resonance is the tendency of a mechanical system to respond at greater amplitude when the frequency of its oscillations matches the system's natural frequency of vibration (its resonance frequency or resonant frequency) than it does at other frequencies. It may cause violent swaying motions and even catastrophic failure in improperly constructed structures including bridges, buildings and airplanes—a phenomenon known as resonance disaster.

Various examples of mechanical resonance include:-

  • Most clocls keep time by mechanical resonance in a balance wheel, pendulum, or quartz crystal.
  • The resonance of the basilar membranein the ear.
  • Making a child's swing swing higher by pushing it at each swing.
  • A wineglass breaking when someone sings a loud note at exactly the right pitch.

 A mechanical system is oscillating at resonance with a constant amplitude. Which one of the following statements is not correct?

resonance oscillations physics

  1. The applied force prevents the amplitude from becoming too large.

  2. The frequency of the applied force is the same as the natural frequency of oscillation of the system.

  3. The total energy of the system is constant.

  4. The amplitude of oscillations depends on the amount of damping.

Show answer
Correct Option: A
Explanation:

The applied force prevents the amplitude from becoming too large.


Option A is correct.

Which of the following is an example of acoustic resonance?

resonance oscillations physics

  1. Feedback in guitars

  2. A pendulum

  3. Nuclear magnetic resonance

  4. A swing

Show answer
Correct Option: A
Explanation:

$Answer:-$ A

Acoustic resonance is a phenomenon that consists of a given acoustic system amplifying a sound whose frequency matches one of its own natural frequencies of vibration (its resonance frequencies).
The resonance of a tube of air is related to the length of the tube, its shape, and whether it has closed or open ends. Musically useful tube shapes are conical and cylindrical . A pipe that is closed at one end is said to be stopped while an open pipe is open at both ends. Modern orchestral flutes behave as open cylindrical pipes; clarinets and lip-reed instruments (brass instruments) behave as closed cylindrical pipes; and saxophones, bassoons as closed conical pipes. Vibrating air columns also have resonances at harmonics, like strings (in guitars).

Destruction of buildings during an earthquake is an example of:

resonance oscillations physics

  1. mechanical resonance

  2. beats

  3. damped vibration

  4. critical vibration

Show answer
Correct Option: A
Explanation:

During earthquake, when the frequency of earthquake becomes equal to the natural frequency of building, resonance (mechanical) occurs due to which amplitude of vibration of building increases and building get destroy.

Which of the following shows mechanical resonance?

resonance oscillations physics

  1. Balance wheel

  2. Pendulum

  3. Quartz crystal

  4. All of the above

Show answer
Correct Option: D
Explanation:

$Answer:-$ D

Mechanical resonance is the tendency of a mechanicalsystem to respond at greater amplitude when the frequency of its oscillations matches the system's natural frequency of vibration (its resonance frequency or resonant frequency) than it does at other frequencies.
examples: Most clocks keep time by mechanical resonance in a balance wheel, pendulum, or quartz crystal.

Which of the following shows acoustic resonance?

resonance oscillations physics

  1. Harps

  2. Guitars

  3. Pianos

  4. Crystal quarts

Show answer
Correct Option: A,B,C
Explanation:

$Aswer:-$ A,B,C

Acoustic resonance is a phenomenon that consists of a givenacoustic system amplifying a sound whose frequency matches one of its own natural frequencies of vibration (its resonancefrequencies).
Acoustic resonance is an important consideration for instrument builders, as most acoustic instruments use resonators, such as the strings and body of a violin, the length of tube in a flute, and the shape of a drum membrane.
In quartz crystals mechanical resonance occurs.

Pushing a person in a swing is a common example of which type of resonance?

resonance oscillations physics

  1. Mechanical resonance

  2. Acoustic resonance

  3. Tidal resonance

  4. None of the above

Show answer
Correct Option: A
Explanation:

When we push a person in a swing, we generally match the time between two consecutive pushes, with the time, in which swing comes back to its extreme position. In fact we match our pushing frequency with the frequency of swing to get large arc of swing (amplitude), this is a common example of mechanical resonance.