Oscillations

A mass attached to a spring is free to oscillate, with angular velocity \omega, in a horizontal plane without friction or damping. It is pulled to a distance x_{0} and pushed towards the centre with a velocity v_{0} at time t=0 . Determine the amplitude of the resulting oscillations in terms of the parameters \omega, x_{0} and v_{0} . [Hint: Start with the equation x=a \cos (\omega t+\theta) and note that the initial velocity is negative.]

The angular velocity of the spring be $\omega$ $x=a \cos (\omega t+\theta)$ At $t=0, x=x_{0}$ On Substituting these values in the above equation we get, $\mathrm{x}_{0}=\mathrm{A} \cos \theta-(1)$...

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A circular disc of mass 10 \mathrm{~kg} is suspended by a wire attached to its centre. The wire is twisted by rotating the disc and released. The period of torsional oscillations is found to be 1.5 s. The radius of the disc is 15 \mathbf{c m}. Determine the torsional spring constant of the wire. (Torsional spring constant \alpha is defined by the relation \mathrm{J}=-\alpha \theta, where \mathrm{J} is the restoring couple and \theta the angle of twist).

Mass of the circular disc is given as $10 \mathrm{~kg}$ Period of torsional oscillation is given as $1.5 \mathrm{~s}$ Radius of the disc is given as $15 \mathrm{~cm}=0.15 \mathrm{~m}$ Restoring...

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You are riding in an automobile of mass 3000 \mathrm{~kg}. Assuming that you are examining the oscillation characteristics of its suspension system. The suspension sags 15 \mathrm{~cm} when the entire automobile is placed on it. Also, the amplitude of oscillation decreases by 50 \% during one complete oscillation. Estimate the values of (a) the spring constant \mathbf{k} and (b) the damping constant b for the spring and shock absorber system of one wheel, assuming that each wheel supports 750 \mathrm{~kg}.

(a) Mass of the automobile is given as $=3000 \mathrm{~kg}$ The suspension sags by a length of $15 \mathrm{~cm}$ Decrease in amplitude $=50 \%$ during one complete oscillation If each spring's...

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An air chamber of volume V has a neck area of cross-section into which a ball of mass m just fits and can move up and down without any friction. Show that when the ball is pressed down a little and released, it executes SHM. Obtain an expression for the time period of oscillations assuming pressure-volume variations of air to be isothermal [see Figure]

Solution: Volume of the air chamber is given as $\mathrm{V}$ Cross-sectional area of the neck is given as $\mathrm{A}$ Mass of the ball be $m$ The ball is fitted in the neck at position given as...

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One end of a U-tube containing mercury is connected to a suction pump and the other end to atmosphere. A small pressure difference is maintained between the two columns. Show that, when the suction pump is removed, the column of mercury in the U-tube executes simple harmonic motion.

Area of cross-section of the U-tube is given as $A$ Density of the mercury column is given as $\rho$ Acceleration due to gravity is given as $g$ Restoring force, F = Weight of the mercury column of...

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A cylindrical piece of cork of density of base area A and height h floats in a liquid of density \rho_{1}. The cork is depressed slightly and then released. Show that the cork oscillates up and down simple harmonically with a period \mathrm{T}=2 \pi \sqrt{\mathrm{h}} \rho / \rho_{1} \mathrm{~g} where \rho is the density of cork. (Ignore damping due to viscosity of the liquid)

Base area of the cork is given as $=\mathrm{A}$ Height of the cork is given as $h$ Density of the liquid is given as $\rho_{1}$ Density of the cork is given as $\rho$ In equilibrium: Weight of the...

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A simple pendulum of length I and having a bob of mass M is suspended in a car. The car is moving on a circular track of radius \mathbf{R} with a uniform speed \mathbf{v} . If the pendulum makes small oscillations in a radial direction about its equilibrium position, what will be its time period?

The centripetal acceleration supplied by the circular motion of the car, as well as the acceleration due to gravity, will be felt by the bob of the basic pendulum. Acceleration due to gravity is...

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Answer the following questions:
(a) A man with a wristwatch on his hand falls from the top of a tower. Does the watch give the correct time during the free fall?
(b) What is the frequency of oscillation of a simple pendulum mounted in a cabin that is freely falling under gravity?

(a) Wristwatches work on the principle of spring action and are not affected by gravity's acceleration. As a result, the time on the watch will be accurate. (b) The cabin's acceleration owing to...

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Answer the following questions:
(a) Time period of a particle in SHM depends on the force constant k and mass m of the particle: \mathbf{T}==2 \pi(\sqrt{m} / \sqrt{k}). A simple pendulum executes SHM approximately. Why then is the time period of a pendulum independent of the mass of the pendulum?
(b) The motion of a simple pendulum is approximately simple harmonic for small-angle oscillations. For larger angles of oscillation, a more involved analysis shows that \mathbf{T} is greater than 2 \pi(\sqrt{I} / \sqrt{g}) . Think of a qualitative argument to appreciate this result.

(a) The spring constant $k$ is proportional to the mass in the case of a simple pendulum. The numerator ($m$) and denominator ($d$) will cancel each other out. As a result, the simple pendulum's...

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Figure (a) shows a spring of force constant k clamped rigidly at one end and a mass \mathbf{m} attached to its free end. A force F applied at the free end stretches the spring. Figure (b) shows the same spring with both ends free and attached to a mass m at either end. Each end of the spring in Fig. (b) is stretched by the same force F.

(a) What is the maximum extension of the spring in the two cases? (b) If the mass in Fig. (a) and the two masses in Fig. (b) is released, what is the period of oscillation in each case? Solution:...

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Plot the corresponding reference circle for each of the following simple harmonic motions. Indicate the initial (t=0) position of the particle, the radius of the circle, and the angular speed of the rotating particle. For simplicity, the sense of rotation may be fixed to be anticlockwise in every case: ( x is in cm and \mathrm{t} is in \mathrm{s}).
(a) x=3 \sin (2 \pi t+\pi / 4)(b) x=2 \cos \pi t

(a)$x=3 \sin (2 m t+\pi / 4)$ $=-3 \cos (2 \pi t+\pi / 4+\pi / 2)$ $=-3 \cos (2 \pi t+3 \pi / 4)$ $=-3 \cos (2 \pi t+3 \pi / 4)$ On comparing with the standard equation $A \cos (\omega t+\Phi)$, we...

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Plot the corresponding reference circle for each of the following simple harmonic motions. Indicate the initial (t=0) position of the particle, the radius of the circle, and the angular speed of the rotating particle. For simplicity, the sense of rotation may be fixed to be anticlockwise in every case: ( x is in cm and \mathrm{t} is in \mathrm{s}).
(a) x=-2 \sin (3 t+\pi / 3)
(b) x=\cos (\pi / 6-t)

(a) $x=-2 \sin (3 t+\pi / 3)$ $=2 \cos (3 t+\pi / 3+\pi / 2)$ $=2 \cos (3 t+5 \pi / 6)$ On comparing the above equation with the standard equation, $x=A \cos (\omega t+\Phi)$, Amplitude will be $A=2...

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In the given figure, let us take the position of mass when the spring is unstreched as x=0, and the direction from left to right as the positive direction of x-axis. Give x as a function of time t for the oscillating mass if at the moment we start the stopwatch (t =0), the mass is at the maximum compressed position. In what way do these functions for SHM differ from each other, in frequency, in amplitude or the initial phase?

Solution: The body is in the left position at maximal compression, with an initial phase of $3 \pi / 2$ rad. Then, $x=a \sin (\omega t+3 \pi / 2)$ $=-a \cos \omega t$ $=-2 \cos 20 t$ As a result,...

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In the given figure, let us take the position of mass when the spring is unstreched as x=0, and the direction from left to right as the positive direction of x-axis. Give x as a function of time t for the oscillating mass if at the moment we start the stopwatch (t =0), the mass is
(a) at the mean position,
(b) at the maximum stretched position.

Solution: Distance travelled by the mass sideways is given as $a=2.0 \mathrm{~cm}$ Angular frequency of oscillation can be calculated as, $\omega=\sqrt{k} / \mathrm{m}$ $=\sqrt{1200 / 3}$...

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The motion of a particle executing simple harmonic motion is described by the displacement function, x(t)=A \cos (\omega t+\varphi) If the initial (t =0 ) position of the particle is 1 \mathrm{~cm} and its initial velocity is \omega \mathrm{cm} / \mathrm{s}, what are its amplitude and initial phase angle? The angular frequency of the particle is \pi \mathrm{s}^{-1}. If instead of the cosine function, we choose the sine function to describe the SHM: x=B \sin (w t+a), what are the amplitude and initial phase of the particle with the above initial conditions. Solution:

At positlon, t = 0, The given function is $x(t)=A \cos (\omega t+\phi).....(1)$ $\begin{array}{l} 1=A \cos (\omega \times 0+\phi)=A \cos \phi \\ A \cos \phi=1 \end{array}$ Differentiating equation...

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A particle is in linear simple harmonic motion between two points, A and B, 10 \mathrm{~cm} apart. Take the direction from A to B as the positive direction and give the signs of velocity, acceleration and force on the particle when it is
(a) at 3 \mathrm{~cm} away from A going towards \mathrm{B}, and
(b) at 4 \mathbf{c m} away from B going towards A.

(a) Positive, Positive, Positive From the end $A$, the particle is travelling toward point 0. This motion is going from $A$ to $B$, which is the standard positive direction. As a result, the...

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A particle is in linear simple harmonic motion between two points, A and B, 10 \mathrm{~cm} apart. Take the direction from A to B as the positive direction and give the signs of velocity, acceleration and force on the particle when it is
(a) at the mid-point of AB going towards A,
(b) at 2 \mathbf{c m} away from B going towards A

(a) Negative, Zero, Zero A basic harmonic motion is being performed by the particle. The particle's mean location is denoted by $O$. Its highest velocity is at the mean position $O$. Because the...

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A particle is in linear simple harmonic motion between two points, A and B, 10 \mathrm{~cm} apart. Take the direction from A to B as the positive direction and give the signs of velocity, acceleration and force on the particle when it is
(a) at the end A,
(b) at the end B

(a) Zero, Positive, Positive Points A and B are the path's two ends, with A-B=10cm and'O' being the path's halfway. Between the end locations, a particle moves in a linear simple harmonic motion....

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Which of the following examples represent (nearly) simple harmonic motion and which represent periodic but not simple harmonic motion?
(a) motion of a ball bearing inside a smooth curved bowl, when released from a point slightly above the lower most point.
(b) general vibrations of a polyatomic molecule about its equilibrium position.

(a) Simple harmonic motion (b) SHM is not periodic, although general vibrations of a polyatomic molecule about its equilibrium position are. The inherent frequencies of a polyatomic molecule are...

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