(a) Find numerical values of the constants and computer plot together on the same axes graphs of (5.30),(5.31) and (5.32) in order to compare overdamped, critically damped, and oscillatory motion. Suggested numbers: Let \(\omega=1,\) and \(b=13 / 5,1,5 / 13\) for the three kinds of motion. Let \(y(0)=1\) and \(y^{\prime}(0)=0\). (b) Repeat the problem with the same set of \(\omega\) and \(b\) values and with \(y(0)=1\) but with \(y^{\prime}(0)=1\). (c) Again repeat, with \(y^{\prime}(0)=-1\).

Short Answer

Expert verified
Solve the differential equation with given parameters, then plot the solutions for each damping case with the specified initial conditions.

Step by step solution

01

Identify Given Parameters

The problem provides \(\omega=1\) and damping constants b as \(\frac{13}{5}\), \(\1\), \(\frac{5}{13}\) for the three types of motion.
02

Formulate the Differential Equation

The general form of the second-order linear differential equation for damped harmonic motion is \(\ddot{y} + 2b\dot{y} + \omega^{2}y = 0\). Given \(\omega=1\), the equation simplifies to \(\ddot{y} + 2b\dot{y} + y = 0\).
03

Initial Conditions

For each scenario, solve the differential equation with the initial conditions provided: \(\y(0)=1\), \(\y^{\prime}(0)=0\); \(\y(0)=1\), \(\y^{\prime}(0)=1\); and \(\y(0)=1\), \(\y^{\prime}(0)=-1\).
04

Case 1: Overdamped Motion

For \(\b=\frac{13}{5}\), solve the differential equation \(\ddot{y} + \frac{26}{5}\dot{y} + y = 0\) with the initial conditions.
05

Case 2: Critically Damped Motion

For \(\b=1\), solve the differential equation \(\ddot{y} + 2\dot{y} + y = 0\) with the initial conditions.
06

Case 3: Underdamped Motion

For \(\b=\frac{5}{13}\), solve the differential equation \(\ddot{y} + \frac{10}{13}\dot{y} + y = 0\) with the initial conditions.
07

Plot the Solutions

Plot all three solutions for each scenario on the same axes to compare overdamped, critically damped, and underdamped motions. This involves plotting the functions of time obtained from solving the differential equations.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Differential Equations
Differential equations describe how a quantity changes over time. In this exercise, we deal with a second-order linear differential equation, specifically for damped harmonic motion.
This can be written as: \(\ddot{y} + 2b\dot{y} + \omega^2 y = 0\), where y represents the displacement from an equilibrium position.
Here, \(\ddot{y}\) is the acceleration, \(\dot{y}\) is the velocity, and y is the displacement. The term 2b\dot{y} represents damping (resistance to motion). Depending on the value of b, the system can be overdamped, critically damped, or underdamped.
Initial Conditions
Initial conditions specify the state of the system at the start of observation. They are crucial for solving differential equations because they allow us to find a specific solution that fits a given context. In our problem, we have sets of initial conditions:
\(\begin\{cases\}y(0)=1\ y\prime(0)=0\, y(0)=1\ y\prime(0)=1\, y(0)=1\ y\prime(0)=-1\end\{cases}\).
These initial conditions mean we start with the displacement of 1 and various initial velocities (0, 1, and -1). Solving the differential equation with these will show how the system behaves over time for each scenario.
Mechanical Vibrations
Mechanical vibrations occur when a system oscillates about an equilibrium position. This is often due to forces that try to restore the system to its rest state.
In a damped harmonic oscillator, these vibrations are also influenced by damping, which is a resistance force proportional to the velocity. The damping force reduces the amplitude (height) of the vibrations over time.
Mathematically, mechanical vibrations are described by our differential equation: \(\ddot{y} + 2b\dot{y} + \omega^2 y = 0\). This equation results from Newton’s second law, considering a restoring force proportional to displacement, a damping force proportional to velocity, and an inertial force proportional to acceleration.
Overdamping
Overdamping occurs when the damping constant b is large enough to prevent oscillations. In this case, the system returns to equilibrium without oscillating.
For instance, if \(\b=\frac{13}{5}\), our differential equation becomes \(\ddot{y} + \frac{26}{5}\dot{y} + y = 0\). Solving this will show a smooth, non-oscillatory return to equilibrium.
Overdamped systems take longer to return to equilibrium compared to critically damped systems, as the high damping force initially opposes the motion before gradually letting the displacement reduce.
Critical Damping
Critical damping is the exact amount of damping that allows the system to return to equilibrium as quickly as possible without oscillating. This happens when the damping constant b equals a specific critical value.
In our problem, with \(\b=1\), we get the equation \(\ddot{y} + 2\dot{y} + y = 0\) for critical damping. Solving it shows the fastest return to equilibrium without overshooting.
Critical damping is ideal for systems wanting a quick return to rest, like car shock absorbers, where too much or too little damping would prolong the settling time or cause oscillations.
Underdamping
Underdamping happens when the damping constant b is small and the system oscillates while gradually returning to equilibrium. The amplitude of oscillations decreases over time due to the damping force.
For \(\b=\frac{5}{13}\)\ff, our differential equation becomes \(\ddot{y} + \frac{10}{13}\dot{y} + y = 0\). Solving this shows oscillatory motion with gradually reducing peaks.
Underdamped systems are common in many mechanical and electrical systems where some oscillation is permissible or even desired, such as in clocks or musical instruments.

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Most popular questions from this chapter

(a) Consider a light beam traveling downward into the ocean. As the beam progresses, it is partially absorbed and its intensity decreases. The rate at which the intensity is decreasing with depth at any point is proportional to the intensity at that depth. The proportionality constant \(\mu\) is called the linear absorption coefficient. Show that if the intensity at the surface is \(I_{0},\) the intensity at a distance \(s\) below the surface is \(I=I_{0} e^{-\mu s} .\) The linear absorption coefficient for water is of the order of \(10^{-2} \mathrm{ft}^{-1}\) (the exact value depending on the wavelength of the light and the impurities in the water). For this value of \(\mu,\) find the intensity as a fraction of the surface intensity at a depth of \(1 \mathrm{ft}\), 50 ft, 500 ft, 1 mile. When the intensity of a light beam has been reduced to half its surface intensity \(\left(I=\frac{1}{2} I_{0}\right),\) the distance the light has penetrated into the absorbing substance is called the half-value thickness of the substance. Find the half-value thickness in terms of \(\mu .\) Find the half-value thickness for water for the value of \(\mu\) given above. (b) Note that the differential equation and its solution in this problem are mathematically the same as those in Example 1, although the physical problem and the terminology are different. In discussing radioactive decay, we call \(\lambda\) the decay constant, and we define the half-life \(T\) of a radioactive substance as the time when \(N=\frac{1}{2} N_{0}\) (compare half-value thickness). Find the relation between \(\lambda\) and \(T.\)

For each of the following differential equations, separate variables and find a solution containing one arbitrary constant. Then find the value of the constant to give a particular solution satisfying the given boundary condition. Computer plot a slope field and some of the solution curves. \(2 y^{\prime}=3(y-2)^{1 / 3}, \quad y=3\) when \(x=1\)

Solve the following sets of equations by the Laplace transform method. $$\begin{aligned} &y^{\prime}+2 z=1 \quad y_{0}=0\\\ &2 y-z^{\prime}=2 t \quad z_{0}=1 \end{aligned}$$

By using Laplace transforms, solve the following differential equations subject to the given initial conditions. $$y^{\prime \prime}+y=\sin t, \quad y_{0}=0, y_{0}^{\prime}=-\frac{1}{2}$$

By using Laplace transforms, solve the following differential equations subject to the given initial conditions. $$y^{\prime \prime}-6 y^{\prime}+9 y=t e^{3 t}, \quad y_{0}=0, y_{0}^{\prime}=5$$

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