/*! 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 101 HARMONIC MOTION The displacement... [FREE SOLUTION] | 91Ó°ÊÓ

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HARMONIC MOTION The displacement from equilibrium of an oscillating weight suspended by a spring and subject to the damping effect of friction is given by \(y(t) = 2e^{-t} cos\ 6t\), where \(y\) is the displacement (in centimeters) and \(t\) is the time (in seconds). Find the displacement when (a) \(t=0\), (b) \(t=\frac{1}{4}\), and \(t=\frac{1}{2}\).

Short Answer

Expert verified
The displacement when (a) \(t=0\) is \(2cm\), when (b) \(t=\frac{1}{4}\) is approximately \(1.35cm\) and when (c) \(t=\frac{1}{2}\) is approximately \(0.22cm\).

Step by step solution

01

Substituting \(t=0\)

To find the displacement when \(t=0\), substitute \(t=0\) into the equation: \(y(0) = 2e^{-0} cos\ 6*0 = 2* cos \ 0\). We know that \(cos \ 0 =1\). Hence, \(y(0) = 2*1 = 2\).
02

Substituting \(t=\frac{1}{4}\)

Next, to find the displacement when \(t=\frac{1}{4}\), substitute \(t=\frac{1}{4}\) into the equation: \(y(\frac{1}{4}) = 2e^{-\frac{1}{4}} cos\ 6*\frac{1}{4} = 2e^{-\frac{1}{4}} cos \ \frac{3}{2}\). Here, you would need to calculate the values for \(e^{-\frac{1}{4}}\) and \(cos \ \frac{3}{2}\) using a scientific calculator.
03

Substituting \(t=\frac{1}{2}\)

Finally, to find the displacement when \(t=\frac{1}{2}\), substitute \(t=\frac{1}{2}\) into the equation: \(y(\frac{1}{2}) = 2e^{-\frac{1}{2}} cos\ 6*\frac{1}{2} = 2e^{-\frac{1}{2}} cos \ 3\). Again, you must use a scientific calculator to compute the values of \(e^{-\frac{1}{2}}\) and \(cos \ 3\).

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Key Concepts

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

Damping Effect
When discussing harmonic motion in physics, the damping effect is a critical concept to understand. It refers to the phenomenon that causes an oscillating system, like a spring with a weight attached, to gradually lose energy over time. This is usually due to resistive forces such as friction or air resistance.

In the context of the given exercise, the presence of a damping effect is represented by the exponential term, \(e^{-t}\), in the displacement equation \(y(t) = 2e^{-t} \cos 6t\). The value of \(e^{-t}\) decreases as time \(t\) increases, which exemplifies how the oscillation amplitude is reduced due to damping.

The practical understanding of the damping effect is crucial in engineering and other sciences where managing vibrations is important. For instance, vehicle suspension systems are designed to absorb shocks and vibrations, providing a smoother ride, and are a prime example of damping in action.
Oscillating Systems
Oscillating systems are pervasive in nature and technology, and understanding them is essential for students of physics and engineering. These systems move or 'oscillate' back and forth around an equilibrium position. Common examples include pendulums, guitar strings, and, as our exercise depicts, weights attached to springs.

The exercise illustrates an oscillating weight on a spring described by a cosine function, \( \cos 6t\), which is a fundamental trigonometric function representing periodic motion. The cosine function reflects the repetitive nature of the oscillation with a frequency determined by the coefficient of \(t\), in this case, 6. This coefficient is related to how often the weight completes an oscillation cycle in a given time period. The study of oscillating systems leads to a deeper understanding of waves, sound, and many other physical phenomena.
Exponential Decay
Exponential decay is a process where a quantity decreases at a rate proportional to its current value, resulting in a rapid decrease that slows over time. It's a fundamental concept seen across various scientific fields, including physics, chemistry, and even finance. In our exercise, it is expressed as the \(e^{-t}\) component of the harmonic motion equation.

The significance of exponential decay in this context lies in its role in damping. As time increases, the exponential term \(e^{-t}\) approaches zero, reflecting the decrease in amplitude of the oscillating weight on the spring due to energy loss. By combining this with the cosine function in the exercise, \(y(t) = 2e^{-t} \cos 6t\), we can visualize how the displacement diminishes over time, embodying the real-world behavior of decaying oscillations.

Moreover, the concept of exponential decay isn't limited to oscillations; it's also used to describe radioactive decay, population decline, and cooling of objects. Grasping this concept allows students to comprehend a wide array of phenomena that can be described mathematically by similar exponential functions.

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Most popular questions from this chapter

HARMONIC MOTION In Exercises 57-60, for the simple harmonic motion described by the trigonometric function, find (a) the maximum displacement, (b) the frequency, (c ) the value of \(d\) when \(t=5\), and (d) the least positive value of \(d\) for which \(t=5\). Use a graphing utility to verify your results. \(d\ =\ \dfrac{1}{64} sin\ 792 \pi t\)

SPEED ENFORCEMENT A police department has setup a speed enforcement zone on a straight length of highway. A patrol car is parked parallel to the zone, 200 feet from one end and 150 feet from the other end (see figure). (a) Find the length \(l\) of the zone and the measures of the angles \(A\) and \(B\) (in degrees). (b) Find the minimum amount of time (in seconds) it takes for a vehicle to pass through the zone without exceeding the posted speed limit of 35 miles per hour.

AIRPLANE ASCENT During takeoff, an airplane's angle of ascent is \(18^\circ\) and its speed is 275 feet per second. (a) Find the plane's altitude after 1 minute. (b) How long will it take the plane to climb to an altitude of 10,000 feet?

DATA ANALYSIS The number of hours \(H\) of daylight in Denver, Colorado on the 15th of each month are: \(1(9.67)\), \(2(10.72)\), \(3(11.92)\), \(4(13.25)\), \(5(14.37)\), \(6(14.97)\), \(7(14.72)\), \(8(13.77)\), \(9(12.48)\), \(10(11.18)\), \(11(10.00)\), \(12(9.38)\). The month is represented by \(t\), with \(t=1\) corresponding to January. A model for the data is given by \(H(t)\ =\ 12.13\ +\ 2.77\ sin[(\pi t/6)\ -\ 1.60]\). (a) Use a graphing utility to graph the data points and the model in the same viewing window. (b) What is the period of the model? Is it what you expected? Explain. (c) What is the amplitude of the model? What does it represent in the context of the problem? Explain.

In Exercises 55-66, find the exact value of the expression. (Hint:Sketch a right triangle.) \(cot(arctan\ \frac{5}{8})\)

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