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Unformatted text preview: HOMEWORK: Week 13 Chapter 14- SOLUTIONS (14.2) A surfer floating beyond the breakers notes 14 waves per minute passing his position. If the wavelength of these waves is 34 m, what is their speed? SOLUTION 2 (34 m)(14 Hz) 4.8 10 m s v f = = = (14.12) Two steel guitar strings have the same length. String A has a diameter of 0.50 mm and is under 410.0 N of tension. String B has a diameter of 1.0 mm and is under a tension of 820.0 N. Find the ratio of the wave speeds, v v A B / , in these two strings. SOLUTION , F v = and a doubled diameter means a quadrupled cross-sectional area, thus a quadrupled mass per length, . A A B B A B A B 4.0 410 N 4.0 820 N 1.4 v F v F F F = = = = (14.16) A wave on a string is described by the following equation: y x t = F H G I K J 15 50 12 cm cos cm s b g . (a) What is the amplitude of this wave? (b) What is its wavelength? (c) What is its period? (d) What is its speed? (e) In which direction does the wave travel? SOLUTION The form is 2 2 cos . y A x t T = (a) A = 15 cm (b) 2 , 5.0 cm = so 10 cm = (c) 2 , 12 s T = so T = 24 s (d) 10 cm 0.42 cm s 24 s v f T = = = = (e) To the right, because the t-term has the opposite sign of the x-term. (14.20) Dolphins of the open ocean are classified as Type II Odontocetes (toothed whales). These animals use ultrasonic clicks with a frequency of about 55 kHz to navigate and find prey. (a) Suppose a dolphin sends out a series of clicks that are reflected back from the bottom of the ocean 75 m below. How much time elapses before the dolphin hears the echoes of the below....
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