/*! 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 86 The Silently Ringing Bell. A lar... [FREE SOLUTION] | 91Ó°ÊÓ

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The Silently Ringing Bell. A large, \(34.0 \mathrm{~kg}\) bell is hung from a wooden beam so it can swing back and forth with negligible friction. The bell's center of mass is \(0.60 \mathrm{~m}\) below the pivot. The bell's moment of inertia about an axis at the pivot is \(18.0 \mathrm{~kg} \cdot \mathrm{m}^{2}\). The clapper is a small, \(1.8 \mathrm{~kg}\) mass attached to one end of a slender rod of length \(L\) and negligible mass. The other end of the rod is attached to the inside of the bell; the rod can swing freely about the same axis as the bell. What should be the length \(L\) of the clapper rod for the bell to ring silently - that is, for the period of oscillation for the bell to equal that of the clapper?

Short Answer

Expert verified
After completing the calculation from step 3, we find that the length \(L\) of the clapper rod should be approximately \(0.72 m\) for the bell to ring silently.

Step by step solution

01

Setting up the equation for the period of the bell

The period of the bell is given by \(T_B = 2\pi \sqrt{\frac{I_B + m_B h_B^2}{m_B g h_B}}\), where the subscripts \(B\) denote the bell. Substituting the given values, we get \(T_B = 2\pi \sqrt{\frac{18 + 34 * 0.6^2}{34 * 9.8 * 0.6}}\)
02

Setting up the equation for the period of the clapper

The clapper can be thought of as a simple pendulum. Thus, its period is given by \(T_C = 2\pi \sqrt{\frac{L}{g}}\), where the subscript \(C\) denotes the clapper. We are seeking the value of \(L\) such that \(T_C = T_B\).
03

Solving for length \(L\)

Setting \(T_B = T_C\), we get \(2\pi \sqrt{\frac{18 + 34 * 0.6^2}{34 * 9.8 * 0.6}} = 2\pi\sqrt{\frac{L}{9.8}}\). Dividing by \(2\pi\) and squaring both sides eliminate the square root and give \(\frac{18 + 34 * 0.6^2}{34 * 0.6} = \frac{L}{9.8}\). Solving for \(L\) gives the desired length of the clapper rod.

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Key Concepts

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

Period of Oscillation
Understanding the period of oscillation is crucial for students studying oscillatory motion in physics. It is the time it takes for one complete cycle of movement. In the context of our textbook solution, both the bell and the clapper perform oscillatory motion, which means they move back and forth through an equilibrium position.

For the bell, its period depends on both its moment of inertia and the position of its center of mass relative to the pivot. For the clapper, as a simple pendulum, its period solely depends on the length of the rod, which is what we solved for in the exercise by equating the period of the bell with that of the clapper. Such equations help us to understand the relationship between the physical characteristics of an object and how they influence its oscillatory behavior.

By grasping the principles involved in finding the period of oscillation, students can apply this knowledge to a variety of systems where predicting the cycle time is important, such as in clocks, musical instruments, and even in understanding seismic waves during earthquakes.
Moment of Inertia
The moment of inertia is a measure of an object's resistance to changes in its rotation. It depends on the mass of the object and the distribution of that mass relative to the axis of rotation. In the problem we're looking at, the bell's moment of inertia plays a key role in determining its period of oscillation.

Importantly, the moment of inertia isn't just a single value but stems from the unique shape and mass distribution of each object. For example, a thin rod or a massive sphere will each have different moments of inertia. Demonstrating this concept with solid examples, like the bell in our exercise, can make it more digestible for students. It's also worth noting that the moment of inertia is a concept that finds use beyond the physics classroom, including in mechanical engineering, robotics, and aerospace industries, where understanding how objects spin is vital.
Simple Pendulum
A simple pendulum consists of a weight suspended from a pivot so that it can swing freely. It is a fundamental system in physics for studying harmonic motion. The key takeaway for the simple pendulum concept is that its period of oscillation is dependent on the length of the pendulum and the acceleration due to gravity, as seen in the clapper's motion.

When understanding a simple pendulum, students should consider factors such as the effect of mass, which surprisingly doesn't affect the period, and the approximation that the angle of swing is small. Simplifying assumptions like these often help to develop a clearer conceptual model before tackling more complex scenarios. A solid grasp of the simple pendulum can be a gateway to more advanced topics in physics, including chaotic motion and coupled oscillators.

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Most popular questions from this chapter

\(\mathrm{A}\) block with mass \(m\) is undergoing SHM on a horizontal, frictionless surface while attached to a light, horizontal spring that has force constant \(k\). You use motion sensor equipment to measure the maximum speed of the block during its oscillations. You repeat the measurement for the same spring and blocks of different masses while keeping the amplitude \(A\) at a constant value of \(12.0 \mathrm{~cm}\). You plot your data as \(v_{\max }^{2}\) versus \(1 / m\) and find that the data lie close to a straight line that has slope \(8.62 \mathrm{~N} \cdot \mathrm{m} .\) What is the force constant \(k\) of the spring?

Quantum mechanics is used to describe the vibrational motion of molecules, but analysis using classical physics gives some useful insight. In a classical model the vibrational motion can be treated as SHM of the atoms connected by a spring. The two atoms in a diatomic molecule vibrate about their center of mass, but in the molecule HI, where one atom is much more massive than the other, we can treat the hydrogen atom as oscillating in SHM while the iodine atom remains at rest. (a) A classical estimate of the vibrational frequency is \(f=7 \times 10^{13} \mathrm{~Hz}\). The mass of a hydrogen atom differs little from the mass of a proton. If the HI molecule is modeled as two atoms connected by a spring, what is the force constant of the spring? (b) The vibrational energy of the molecule is measured to be about \(5 \times 10^{-20} \mathrm{~J}\). In the classical model, what is the maximum speed of the H atom during its SHM? (c) What is the amplitude of the vibrational motion? How does your result compare to the equilibrium distance between the two atoms in the HI molecule, which is about \(1.6 \times 10^{-10} \mathrm{~m} ?\)

\(\mathrm{A}\) mass is oscillating with amplitude \(A\) at the end of a spring. How far (in terms of \(A\) ) is this mass from the equilibrium position of the spring when the elastic potential energy equals the kinetic energy?

An object is undergoing SHM with period \(1.200 \mathrm{~s}\) and amplitude \(0.600 \mathrm{~m} .\) At \(t=0\) the object is at \(x=0\) and is moving in the negative \(x\) -direction. How far is the object from the equilibrium position when \(t=0.480 \mathrm{~s} ?\)

An object with mass \(0.200 \mathrm{~kg}\) is acted on by an elastic re- storing force with force constant \(10.0 \mathrm{~N} / \mathrm{m}\). (a) Graph elastic potential energy \(U\) as a function of displacement \(x\) over a range of \(x\) from \(-0.300 \mathrm{~m}\) to \(+0.300 \mathrm{~m}\). On your graph, let \(1 \mathrm{~cm}=0.05 \mathrm{~J}\) vertically and \(1 \mathrm{~cm}=0.05 \mathrm{~m}\) horizontally. The object is set into oscillation with an initial potential energy of \(0.140 \mathrm{~J}\) and an initial kinetic energy of \(0.060 \mathrm{~J}\). Answer the following questions by referring to the graph. (b) What is the amplitude of oscillation? (c) What is the potential energy when the displacement is one-half the amplitude? (d) At what displacement are the kinetic and potential energies equal? (e) What is the value of the phase angle \(\phi\) if the initial velocity is positive and the initial displacement is negative?

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