Oscillation - NEET Physics Questions
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Oscillation

Question 1: moderate

A simple harmonic motion has an amplitude A and time period T. The time required by it to travel from x = A to x = A/2 is :

1. T/6
2. T/4
3. T/3
4. T/12
View Answer

To find the time required for a particle in Simple Harmonic Motion (SHM) to travel from \( x = A \) to \( x = \frac{A}{2} \), we can use the following steps:

1. Angular Frequency (\( \omega \)):
\[
\omega = \frac{2\pi}{T}
\]

2. Displacement in SHM:
The position \( x(t) \) in SHM can be described by:
\[
x(t) = A \cos(\omega t)
\]

3. Finding Time for Positions:
- For \( x = A \):
\[
A \cos(\omega t_1) = A;  \cos(\omega t_1) = 1 ; t_1 = 0
\]

- For \( x = \frac{A}{2} \):
\[
\frac{A}{2} = A \cos(\omega t_2 ; \cos(\omega t_2) = \frac{1}{2} ; \omega t_2 = \frac{\pi}{3}
\]
\[
t_2 = \frac{\pi}{3\omega} = \frac{\pi T}{6}
\]

4. Time Interval:
The time taken to travel from \( x = A \) to \( x = \frac{A}{2} \) is:
\[
\Delta t = t_2 - t_1 = \frac{\pi T}{6} - 0 = \frac{T}{6}
\]

Thus, the time required to travel from \( x = A \) to \( x = \frac{A}{2} \) is:
\[{\frac{T}{6}}
\]

Question 2: moderate

A particle is executing SHM with amplitude A and has maximum velocity V0. Its speed at displacement A/2 will be

1. (√3)V0/2
2. V0/√2
3. V0
4. V0/4
View Answer

In Simple Harmonic Motion (SHM), the relationship between displacement, velocity, and amplitude can be described using the following equations.

1. The maximum speed \( V_0 \) is given by:
\[
V_0 = \omega A
\]
where \( \omega \) is the angular frequency.

2. The speed \( v \) at a displacement \( x \) in SHM is given by the formula:
\[
v = \sqrt{V_0^2 - \left(\frac{\omega x}{\omega A}\right)^2}
\]
Simplifying this using \( \omega = \frac{V_0}{A} \):
\[
v = \sqrt{V_0^2 - \left(\frac{V_0}{A} \cdot x\right)^2}
\]
Substituting \( x = \frac{A}{2} \):
\[
v = \sqrt{V_0^2 - \left(\frac{V_0}{A} \cdot \frac{A}{2}\right)^2}
\]
\[
v = \sqrt{V_0^2 - \left(\frac{V_0}{2}\right)^2}
\]
\[
v = \sqrt{V_0^2 - \frac{V_0^2}{4}} = \sqrt{\frac{3V_0^2}{4}} = \frac{\sqrt{3}}{2} V_0
\]

Thus, the speed of the particle at displacement \( \frac{A}{2} \) is:
\[{\frac{\sqrt{3}}{2} V_0}
\]

Question 3: moderate

The instantaneous displacement of a simple harmonic oscillator is given by :

y = Acos (ωt + π/4) .

Its speed will be maximum at the time

1. 2π/ω
2. ω/2π
3. ω/π
4. π/4ω
View Answer

For the SHM given by:

\[
y = A \cos(\omega t + \frac{\pi}{4})
\]

Solution:

1. Velocity: The velocity \( v \) is the derivative of \( y \) with respect to \( t \):
\[
v = \frac{dy}{dt} = -A \omega \sin(\omega t + \frac{\pi}{4})
\]

2. Maximum Speed: The speed will be maximum when \( \sin(\omega t + \frac{\pi}{4}) = \pm 1 \).

Therefore,
\[
\omega t + \frac{\pi}{4} = \frac{\pi}{2}
\]

3. Solving for \( t \):
\[
\omega t = \frac{\pi}{2} - \frac{\pi}{4} = \frac{\pi}{4}
\]

\[
t = \frac{\pi}{4\omega}
\]

Answer:
The speed will be maximum at \( t = \frac{\pi}{4\omega} \).

Question 4: moderate

A particle is executing SHM. Then, the graph of velocity as a function of displacement is a/an :

1. Straight line
2. Circle
3. Ellipse
4. Hyperbola
View Answer

In simple harmonic motion (SHM), the velocity \( v \) and displacement \( x \) of a particle are related by:

\[
v = \pm \sqrt{\omega^2 A^2 - \omega^2 x^2}
\]

where:
- \( \omega \) is the angular frequency,
- \( A \) is the amplitude.

 Solution:

1. Rearranging this equation, we get:
\[
\frac{v^2}{\omega^2 A^2} + \frac{x^2}{A^2} = 1
\]

2. This is the equation of an ellipse in the \( v \)-\( x \) plane.

Answer:
The graph of velocity as a function of displacement for a particle in SHM is an ellipse.

Question 5: moderate

The simple harmonic motion of a particle is represented by the equation, x = 4 cos [88t +π/4]. The frequency (in Hz) and the initial displacement (in m) of the particle are

1. 14 : 2√2
2. 16; 2√2
3. 14; 3√2
4. 16; 3√2
View Answer

Given the SHM equation:

\[
x = 4 \cos(88t + \frac{\pi}{4})
\]

Solution:

1. Frequency: The general form of SHM is \( x = A \cos(\omega t + \phi) \), where \( \omega = 2 \pi f \) (angular frequency).

Here, \( \omega = 88 \).

\[
f = \frac{\omega}{2 \pi} = \frac{88}{2 \pi} = 14 \, \text{Hz}
\]

2. Initial Displacement: The initial displacement \( x_0 \) is the value of \( x \) at \( t = 0 \).

Substitute \( t = 0 \) into the equation:
\[
x_0 = 4 \cos\left(\frac{\pi}{4}\right) = 4 \cdot \frac{\sqrt{2}}{2} = 2 \sqrt{2} \, \text{m}
\]

Answer:
The frequency is  14 Hz, and the initial displacement is \( 2 \sqrt{2} \, \text{m} \).

Question 6: moderate

The displacement versus time graph of SHM is as shown in figure :

 

 

 

Which of the following is its acceleration versus time graph ?

1.
2.
3.
4.
View Answer

Equation of y-t graph is : y  = A sin (ωt) differentiating v = A ω cos (ωt) and a= - Aω² sin (ωt) . So the graph is a function of - sin(ωt).

Question 7: moderate

A particle is in linear SHM between two points, A and B, 10 cm apart. Take the direction from A to B as the positive direction, find the signs of velocity, acceleration and force on the particle when it is 4 cm from B going towards A :

1. +, –, +
2. –, +, –
3. –, –, –
4. +, +, +
View Answer

For a particle in simple harmonic motion (SHM), the force and acceleration are always directed towards the equilibrium position (center) and are opposite to the displacement.

Solution:

1. Displacement: Since the particle is 4 cm from \( B \) and moving towards \( A \), it is located closer to \( B \) on the negative side of the equilibrium point. This means the displacement is in the negative direction.

2. Velocity: Since the particle is moving towards \( A \) (the negative direction), its velocity is negative.

3. Acceleration and Force: In SHM, acceleration and force are always directed towards the equilibrium point. Since the particle is on the positive side of the equilibrium (closer to \( B \)), the acceleration and force are in the negative direction.

Conclusion:
The signs of velocity, acceleration, and force are all negative (–, –, –).

Question 8: moderate

A particle executes an undamped SHM of time period T. Then the time period with which the potential energy changes is :

1. T
2. 2T
3. T/2
4. T/4
View Answer

If equation of motion in shm is x = A sin ωt then eqn. of potential energy = ½k x²= ½kA² sin²ωt

\[ U = \frac{1}{2}K A^{2}\left( \frac{1- sin(2\omega t)}{2} \right) \]

Frequency becomes double so time period becomes half.

Question 9: moderate

Two particles execute SHM of same amplitude and frequency along the same straight line. They pass one another when going in opposite directions, each time their displacement is half of their amplitude. The phase difference between them is :

1. 90º
2. 30º
3. 120º
4. 60º
View Answer

Phase difference 2φ= 120 degree

Question 10: moderate

The equation of a simple harmonic motion is given by, y = 3sin π/2 (50t – Φ), where y is in metres and t is in sec, the maximum particle velocity in ms–¹ is :

1. 3 π
2. 50 π
3. 75 π
4. 25 π
View Answer

y = 3sin π/2 (50t - Φ)

\[ \frac{\partial y}{\partial t}= 3 \times \frac{\Pi}{2}\times 50 cos(π/2 (50t - Φ))\] 

Maximum speed = 75 π