Explanation:
The Simple Pendulum. A simple pendulum is defined to have a point mass, also known as the pendulum bob, which is suspended from a string of length L with negligible mass ((Figure)). Here, the only forces acting on the bob are the force of gravity (i.e., the weight of the bob) and tension from the string.
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The frequency of the wave is 
Explanation:
The frequency, the wavelength and the speed of a wave are related by the following equation:

where
c is the speed of the wave
f is the frequency
is the wavelength
For the radio wave in this problem,


Therefore, the frequency is:

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Answer: 1,600 seconds
Explanation:
31,360/9.8 = 3,200.
Then divide 3,200/2 = 1,600
Time = (distance) / (speed)
Time = (150 x 10⁹ m) / (3 x 10⁸ m/s) =
50 x 10¹ sec =
<em>500 sec</em> = 8 min 20 sec