Question

For a certain transverse standing wave on a long string, an antinode is at x = 0 and an adjacent node is at x = 0.20 m. The displacement y(t) of the string particle at x = 0 is shown in the figure, where the scale of the y axis is set by ys = 4.3 cm. When t = 0.90 s, what is the displacement of the string particle at (a) x = 0.30 m and (b) x = 0.40 m ? What is the transverse velocity of the string particle at x = 0.30 m at (c) t = 0.90 s and (d) t = 1.3 s?

Answer 1

The expressions for the traveling and standing wave to find the results for the questions about the displacement and speed of the particle are:

       a) For time zero, the displacement at position x = 0.30 m is y = 3.04 cm

     b) For time zero, the displacement at position x = 0.40 m is: y = 0

      c) For the point x = 0.30 and time t = 0.9s, the velocity of the particle is:

          v = 9.11 cm / s

      d) For the point x = 0.30 and time t = 1.3s, the velocity of the particle is:

          v = 9.65 cm / s

The traveling wave is a disturbance in the medium that moves at constant speed, in the case of a transverse wave the expression for the perpendicular oscillation is:

         y = A sin (kx - wt)

Where y is the oscillation perpendicular to the direction of the displacement, A the amplitude, k in wave number and w the angular velocity.

Standing waves are formed when a traveling wave collides with an obstacle and is reflected, in this case the sum of the two waves gives a wave that does not shift in time and fulfills the relationship

           $\frac{\lambda}{2} = \frac{L}{n}$  

Where λ is the wavelength, L the distance between the reflection points and n the number of nodes.

Indicates that for the standing wave the distance between an antinode and the node is x = 0.20 m, therefore

               $\frac{\lambda}{4} = \frac{L}{1}$  

              λ = 4L

              λ = 4 0.20

              λ = 0.80 m

The wave number.

              k = $\frac{2\pi }{\lambda }$  

              k = $\frac{2 \pi }{0.80 }$  

          ��   k = 2.5π i m⁻¹

In the associated traveling wave, from the graph we can see that the period of the wave is:

             T = 2.8 s

the angular velocity is related to the period.

             $w=\frac{2\pi}{T} \\w = \frac{2\pi }{2.8}$  

             w = 0.714π  rad/s

indicate the maximum displacement that is the amplitude of the wave.

              A = $y_s$  

             A = 4.3 cm

Let's write the equation of the traveling wave.

              y = 4.3 sin [π (2.5 x - 0.714 t)]

with this expression we can answer the questions.

a) the displacement of the particle for x = 0.30 m

            y = 4.3 sin (π (2.5 0.30 - 0.714 t))

            y = 4.3 sin π( 0.75 - 0.714 t(

Remember that the angles must be in radians.  For time t = 0 the displacement is

              y = 4.3  0.707

              y = 3.04 cm

 

b) The displacement for x = 0.4m

              y = 4.3 sin (π 2.5 0.4)

              y = 0 cm

c) the transverse velocity of the wave at x = 0.30 m for the time of t = 0.90s

the speed of the wave is

              $v= \frac{dy}{dt} \\v= A w cos ( kx - wt)$  

              v = 4.3 0.714π cos π(2.5 0.3 - 0.714 t)

              v = 9.65 cos π(0.75 - 0.714 t)

For time t = 0.90 s the velocity is:

            v = 9.65 cos π(0.75 - 0.714 0.9)

            v = 9.65 0.9436

            v = 9.11 cm / s

d) The velocity for time t = 1.3 s

           v = 9.65 cos π(0.75 - 0.714 1.3)

           v = 9.65 0.9999

           v = 9.65 cm / s

In conclusion, using the expressions for the traveling and standing wave, we can find the results for the questions about the displacement and speed of the particle are:

      a) For time zero, the displacement at position x = 0.30 m is y = 3.04 cm

     b) For time zero, the displacement at position x = 0.40 m is: y = 0

      c) For the point x = 0.30 and time t = 0.9s, the velocity of the particle is:

          v = 9.11 cm / s

      d) For the point x = 0.30 and time t = 1.3s, the velocity of the particle is:

          v = 9.65 cm / s

Learn more about traveling waves here: brainly.com/question/15531840