A transverse wave pulse travels to the right along a string with a speed v = 2.0 m/s. At the shape of the pulse is given by the function D = 0.45 cos (2.6x + 1.2), where D and x are in meters. Determine a formula for the wave pulse at any time t assuming there are no frictional losses.

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The given wave pulse is described by the function \( D(x, t=0) = 0.45 \cos(2.6x + 1.2) \), where \( D \) is the displacement, \( x \) is the position, and \( t \) is the time. At \( t = 0 \), this represents the initial shape of the wave pulse.

The wave is traveling to the right with a speed \( v = 2.0 \ \text{m/s} \). For a wave traveling to the right, the general form of the wave equation is \( D(x, t) = D(x - vt, 0) \). This means the wave's shape at any time \( t \) is the same as its initial shape, but shifted to the right by a distance \( vt \).

Substitute \( x - vt \) into the given function for \( x \). The new formula becomes \( D(x, t) = 0.45 \cos(2.6(x - vt) + 1.2) \).

Now substitute the value of \( v = 2.0 \ \text{m/s} \) into the equation. This gives \( D(x, t) = 0.45 \cos(2.6(x - 2.0t) + 1.2) \).

Simplify the expression if needed. The final formula for the wave pulse at any time \( t \) is \( D(x, t) = 0.45 \cos(2.6x - 5.2t + 1.2) \). This equation describes the wave pulse as it propagates to the right without any frictional losses.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Wave Function

A wave function describes the shape and behavior of a wave at any given point in space and time. In this case, the function D = 0.45 cos(2.6x + 1.2) represents a transverse wave pulse, where D is the displacement of the string and x is the position along the string. The cosine function indicates that the wave oscillates, and its parameters determine the wave's amplitude, wavelength, and phase.

Wave Speed

Wave speed is the rate at which a wave propagates through a medium. It is determined by the properties of the medium and is given in this problem as v = 2.0 m/s. Understanding wave speed is crucial for determining how the wave pulse changes over time, as it affects the relationship between the wave's spatial and temporal characteristics.

Time Dependence of Waves

To express the wave pulse as a function of time, we need to incorporate the wave speed into the wave function. The general form of a wave traveling in the positive x-direction can be expressed as D(x, t) = A cos(kx - ωt + φ), where A is amplitude, k is the wave number, ω is the angular frequency, and φ is the phase constant. By substituting the given speed and the wave function parameters, we can derive the time-dependent formula for the wave pulse.