HW2122soln - Physics 21 Fall 2007 Solution to HW-21...

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Physics 21 Fall 2007 Solution to HW-21 K 20-11 A wave travels with speed 220 m/s. Its wave number is 1.50 rad/m. What is its (A) wavelength and (B) frequency? (A) wavenumber k = 2 π / λ , so λ = 2 π /k (B) Use v = f λ . v was given, and λ was calculated in (A). K 20-13 The displacement of a wave traveling in the - y direction is D ( y,t )=4.80cm sin(6.20 y + 61.0 t ), with y in m and t in s. What are the (A) frequency (B) wavelength and (C) speed of this wave? D ( y,t ) = A sin( ky + ϖ t ), k =6.20 and ϖ =61.0 in SI units. (A) ϖ = 2 π f, so f = ϖ /(2 π ) (B) k = 2 π / λ so λ = 2 π / k (C) v = λ f = (2 π / k ) ϖ /(2 π ) = ϖ / k K 20-42 This is a snapshot graph at t =0 of a 5.0 Hz wave traveling to the left. What are (A) the wave speed and (B) phase constant of the wave? K 20-7 The wave speed on a string under tension is190 m/s. What is the speed if the tension T is doubled? From Eq. (3) in Waves Handout,
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HW2122soln - Physics 21 Fall 2007 Solution to HW-21...

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