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Magazine Problem 1
Waves and Energy Transport The intensity of sunlight that reaches Earth's atmosphere is \(1400 \mathrm{W} / \mathrm{m}^{2} .\) What is the intensity of the sunlight that reaches Jupiter? Jupiter is 5.2 times as far from the Sun as Earth. [Hint: Treat the Sun as an isotropic source of light waves.]
Problem 2
Michelle is enjoying a picnic across the valley from a cliff. She is playing
music on her radio (assume it to be an isotropic source) and notices an echo
from the cliff. She claps her hands and the echo takes 1.5 s to return. (a)
Given that the speed of sound in air is \(343 \mathrm{m} / \mathrm{s}\) on that
day, how far away is the cliff? (b) If the intensity of the music $1.0
\mathrm{m}\( from the radio is \)1.0 \times 10^{-5} \mathrm{W} /
\mathrm{m}^{2},$ what is the intensity of the music arriving at the cliff?
Problem 3
The intensity of the sound wave from a jet airplane as it is taking off is
\(1.0 \times 10^{2} \mathrm{W} / \mathrm{m}^{2}\) at a distance of $5.0
\mathrm{m}$ What is the intensity of the sound wave that reaches the ears of a
person standing at a distance of \(120 \mathrm{m}\) from the runway? Assume that
the sound wave radiates from the airplane equally in all directions.
Problem 5
The Sun emits electromagnetic waves (including light) equally in all directions. The intensity of the waves at Earth's upper atmosphere is \(1.4 \mathrm{kW} / \mathrm{m}^{2} .\) At what rate does the Sun emit electromagnetic waves? (In other words, what is the power output?)
Problem 8
When the tension in a cord is \(75 \mathrm{N}\), the wave speed is $140
\mathrm{m} / \mathrm{s} .$ What is the linear mass density of the cord?
Problem 9
A metal guitar string has a linear mass density of $\mu=3.20 \mathrm{g} /
\mathrm{m} .$ What is the speed of transverse waves on this string when its
tension is \(90.0 \mathrm{N} ?\)
Problem 10
Two strings, each \(15.0 \mathrm{m}\) long, are stretched side by side. One
string has a mass of \(78.0 \mathrm{g}\) and a tension of \(180.0 \mathrm{N} .\)
The second string has a mass of \(58.0 \mathrm{g}\) and a tension of $160.0
\mathrm{N} .$ A pulse is generated at one end of each string simultancously.
On which string will the pulse move faster? Once the faster pulse reaches the
far end of its string, how much additional time will the slower pulse require
to reach the end of its string?
Problem 11
A uniform string of length \(10.0 \mathrm{m}\) and weight \(0.25 \mathrm{N}\) is
attached to the ceiling. A weight of \(1.00 \mathrm{kN}\) hangs from its lower
end. The lower end of the string is suddenly displaced horizontally. How long
does it take the resulting wave pulse to travel to the upper end? [Hint: Is
the weight of the string negligible in comparison with that of the hanging
mass?]
Problem 12
Periodic Waves
What is the speed of a wave whose frequency and wavelength are $500.0
\mathrm{Hz}\( and \)0.500 \mathrm{m},$ respectively?
Problem 13
What is the wavelength of a wave whose speed and period are $75.0 \mathrm{m} /
\mathrm{s}\( and \)5.00 \mathrm{ms}$, respectively?
