Please I need help with these questions, I need to study them for my exam. Thank
ID: 1491753 • Letter: P
Question
Please I need help with these questions, I need to study them for my exam. Thanks in advance :)
9. -15 points Walker4 14.P.023 My Notes A wave on a string is described by the following equation (assume the +x direction is to the right) y _ (18 cm) cos(7 mx-1t ) y = (18 crm) cos(-T-x-it 4.1 cm 19 s (a) What is the amplitude of this wave? cm (b) What is its wavelength? cm (c) What is its period? (d) What is its speed? cm/s (e) In which direction does the wave travel? O to the left to the right Submit Answer Save Progress Practice Another Version Submit AnswerSave Progress 10. -/20 points Walker4 14.P.025 My Notes The table below describes four waves by their equations, in which all distances are measured in centimeters and all times are measured in seconds. For each wave, answer the following "yes-no" questions: (a) Does it travel in the +x direction? (b) Does it travel in the -x direction? (c) Does it wave has the highest frequency (of the four waves)? (d) Does it have the greatest wavelength (of the four waves)? (e) Does it have the greatest speed (of the four waves)? wave 11. -1 points Walker4 14.P.026 My Notes At Zion National Park a loud shout produces an echo 17.50 s later from a colorful sandstone cliff. How far away is the cliff?Explanation / Answer
9) A wave on a string is described by the following equation (assume the +x direction is to the right).
y = (18 cm) cos[ x/(4.1 cm) + t/(19 s)]
(a) What is the amplitude of this wave?
A = 18 cm
(b) What is its wavelength?
L = 4.1*2 =8.2 cm
(c) What is its period?
T = 19*2 = 38 s
(d) What is its speed?
v = 8.2/38 = 0.216 cm/s
(e) In which direction does the wave travel?
to the left, because y(x - dx, t+dt) = y(x,t)
10) Consider Acos(nx + mt)
If n and m are both positive or both negative, as t increases x must decrease to stay at the same point on the wave. If n and m are opposite signs, then x will increase as t increases.
period = time for cos function to go through 2pi radians
2*pi = mt
t = 2*pi/m
frequency = 1/t = m/2*pi
wavelength = distance for cos function to go through 2pi radians
2*pi = nx =========> x = 2*pi/n
Speed = distance / time = (2pi/n) / (2pi/m) = m/n
9cos(2x - 19t) Y N N Y Y
7cos(11x - 29t) Y N Y N N
2cos(5x + 7t) Y N N N N
4cos(-17x - 13t) N Y N N N
11) Time for round trip = 344 * 17.5 = 6020 m
Distance to cliff = 6020/2 = 3010 m