/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 56 \(\mathrm{A} 50.0 \mathrm{~g}\) ... [FREE SOLUTION] | 91Ó°ÊÓ

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\(\mathrm{A} 50.0 \mathrm{~g}\) hard-boiled egg moves on the end of a spring with force constant \(k=25.0 \mathrm{~N} / \mathrm{m} .\) Its initial displacement is \(0.300 \mathrm{~m} . \mathrm{A}\) damping force \(F_{x}=-b v_{x}\) acts on the egg, and the amplitude of the motion decreases to \(0.100 \mathrm{~m}\) in \(5.00 \mathrm{~s}\). Calculate the magnitude of the damping constant \(b\).

Short Answer

Expert verified
The magnitude of the damping constant (\(b\)) is \(2.31 \, Ns/m\).

Step by step solution

01

Identify the given values

The given values are the force constant \(k = 25.0 \mathrm{~N/m}\), initial displacement \(A = 0.300 \mathrm{~m}\), future displacement \(A' = 0.100 \mathrm{~m}\) and time \(t = 5.00 \mathrm{~s}\). The damping constant \(b\) is what we want to find.
02

Understand the formula for damping constant

The damping constant (\(b\)) of the damped harmonic oscillator is given by the formula \[b = 2m\left(\frac{ln(A/A')}{t}\right)\] where \(m\) is mass, \(A\) is the initial displacement, \(A'\) is the future displacement, and \(t\) is the time. Here, \(m\) can be calculated using \(m = k/A\).
03

Calculate the mass (\(m\)) of the egg

The force constant (\(k\)) and initial displacement (\(A\)) are used to calculate mass of the egg using the formula \(m = k/A\), that yields \[m = 25.0 \, \text{N/m} / 0.300\, m = 83.3\, kg\].
04

Calculate the damping constant (\(b\))

Substitute the calculated mass (\(m\)) and given values into the equation for the damping constant (\(b\)), \[b = 2( 83.3\, kg)\left(\frac {ln(0.300 \, m / 0.100 \, m)}{5.00 \, s}\right)\] to obtain the damping constant \(b\). On calculation, we get \(b = 2.31 \, Ns/m\).

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Key Concepts

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

Damped Harmonic Oscillator
When we talk about a damped harmonic oscillator, we're focusing on a system in which a mass is attached to a spring, much like the egg in the exercise – except, in this case, the motion is not perpetual. Instead, due to factors such as friction or air resistance, the oscillations of the system decrease over time, leading us to what's called 'damping'. To identify the damping in a system, we can look at the damping constant, represented by the symbol 'b'.

Now imagine a ball rolling across a surface with some friction. Initially, it rolls quickly but eventually comes to a stop. That's damping in action – it removes energy from the system, causing the amplitude of the motion to decrease gradually. In the case of the egg on the spring, the damping force is represented mathematically as a function of velocity, with the damping constant 'b' quantifying the effect. Understanding this concept is crucial in physics as it ties into real-world scenarios like vehicle suspension and earthquake engineering.
Force Constant
The force constant, denoted by 'k' in our problem, is a measure of stiffness of the spring -— the higher the force constant, the stiffer the spring, and the more force required to stretch or compress it by a certain amount. It relates directly to Hooke’s Law, which states that the force required to extend or compress a spring by a distance (x) scales linearly with that distance. The formula is expressed as F = -kx.

For instance, in the exercise, a spring with a force constant of 25.0 N/m is relatively soft, as it doesn't require much force to change its shape. Knowing 'k' allows us to calculate other properties of the system, like the natural frequency of oscillation and the mass if we know the displacement, making it a key concept in oscillatory motion.
Logarithmic Decrement
Logarithmic decrement is a measure of the rate at which the amplitude of a damped oscillator decreases over time. This term might sound quite complex, but it boils down to this: it’s a way to quantify how much the damped oscillations decrease over a number of cycles. It is calculated as the natural logarithm of the ratio of consecutive amplitudes and represented with the delta symbol (Δ). Mathematically, it is expressed as Δ = ln(A1/A2), where A1 and A2 are the amplitudes of two successive peaks.

In real life, logarithmic decrement can tell us how quickly a vibrating structure, like a bridge or building, will settle down after being disturbed. In our egg example, you can think of the decrement as a way to measure 'how much quieter' each bounce of the egg becomes due to the damping effect. It plays a vital role in determining the damping constant 'b' and therefore, impacts the calculations for the damped motion.
Oscillatory Motion Physics
Oscillatory motion is a fundamental concept in physics that refers to the repeated back-and-forth movement of an object about a central point, or equilibrium position. Think of it as the swinging pendulum of a clock or the vibrations of a guitar string. This movement is ruled by restoring forces that pull the system back toward its equilibrium and is characterized by its amplitude, frequency, and period.

Oscillatory systems can be simple, like a mass on a spring (as in our textbook problem), or complex, like the orbits of celestial bodies. Damped oscillations incorporate the effect of energy loss, leading us to consider the medium's resistance and the damping constant. By mastering the principles of oscillatory motion, we gain insights not only into simple mechanical systems but also into the broader workings of the universe, from quantum mechanics to astrophysics.

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Most popular questions from this chapter

In a physics lab, you attach a \(0.200 \mathrm{~kg}\) air-track glider to the end of an ideal spring of negligible mass and start it oscillating. The elapsed time from when the glider first moves through the equilibrium point to the second time it moves through that point is \(2.60 \mathrm{~s}\). Find the spring's force constant.

A uniform, solid metal disk of mass \(6.50 \mathrm{~kg}\) and diameter \(24.0 \mathrm{~cm}\) hangs in a horizontal plane, supported at its center by a vertical metal wire. You find that it requires a horizontal force of \(4.23 \mathrm{~N}\) tangent to the rim of the disk to turn it by \(3.34^{\circ},\) thus twisting the wire. You now remove this force and release the disk from rest. (a) What is the torsion constant for the metal wire? (b) What are the frequency and period of the torsional oscillations of the disk? (c) Write the equation of motion for \(\theta(t)\) for the disk.

SHM of a Floating Object. An object with height \(h\)mass \(M\), and a uniform cross-sectional area \(A\) floats upright in a liquid with density \(\rho\). (a) Calculate the vertical distance from the surface of the liquid to the bottom of the floating object at equilibrium. (b) A downward force with magnitude \(F\) is applied to the top of the object. At the new equilibrium position, how much farther below the surface of the liquid is the bottom of the object than it was in part (a)? (Assume that some of the object remains above the surface of the liquid.) (c) Your result in part (b) shows that if the force is suddenly removed, the object will oscillate up and down in SHM. Calculate the period of this motion in terms of the density \(\rho\) of the liquid, the mass \(M,\) and the cross-sectional area \(A\) of the object. You can ignore the damping due to fluid friction (see Section 14.7).

Four passengers with combined mass \(250 \mathrm{~kg}\) compress the springs of a car with worn-out shock absorbers by \(4.00 \mathrm{~cm}\) when they get in. Model the car and passengers as a single object on a single ideal spring. If the loaded car has a period of vibration of \(1.92 \mathrm{~s}\), what is the period of vibration of the empty car?

A slender rod of length \(80.0 \mathrm{~cm}\) and mass \(0.400 \mathrm{~kg}\) has its center of gravity at its geometrical center. But its density is not uniform; it increases by the same amount from the center of the rod out to either end. You want to determine the moment of inertia \(I_{\mathrm{cm}}\) of the rod for an axis perpendicular to the rod at its center, but you don't know its density as a function of distance along the rod, so you can't use an integration method to calculate \(I_{\mathrm{cm}}\). Therefore, you make the following measurements: You suspend the rod about an axis that is a distance \(d\) (measured in meters) above the center of the rod and measure the period \(T\) (measured in seconds) for small-amplitude oscillations about the axis. You repeat this for several values of \(d\). When you plot your data as \(T^{2}-4 \pi^{2} d / g\) versus \(1 / d\), the data lie close to a straight line that has slope \(0.320 \mathrm{~m} \cdot \mathrm{s}^{2} .\) What is the value of \(I_{\mathrm{cm}}\) for the rod?

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