1. A hiker sees a lightning flash and 15 s later hears the sound of the thunder.
ID: 1381324 • Letter: 1
Question
1. A hiker sees a lightning flash and 15 s later hears the sound of the thunder. Knowing that the speed of sound in air is 1/3 km/s he estimates that the distance to where the lightning occurred is approximately (in km): 2. A cable of length L stretch with tension T vibrates in fundamental mode with frequency f. A second cable from identical wire at the same T that for second harmonic (first overtone) vibrates with frequency 2f has the length: 3. String A and string B have the same length and are stretched with the same tension T. String A weighs twice as much as string B. The ratio of the speed of waves in string A versus B is VA / VB is 4. The distance between two successive antinodes in a wave is:Explanation / Answer
distance = vs*t = (1/3)*15 = 5 km
option B
++++++++++
2)
f = (1/2L)sqrt(T/u)
2f = (1/2L')*sqrt(T/u)
L' = L/2
option A
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3) v = sqrt(/u) = sqrt(T*L/m)
vA/vB = sqrt(mB/mA)
vA/vB = sqrt(1/2) = 0.7
option E
++++++++++++
4)option A
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