Extensional stress. is your answer.
The average speed is 20.8 m/s
Explanation:
The average speed for the trip is given by:

where
d is the distance covered
t is the time elapsed
For the trip in this problem, we have:
d = 187 km = 187,000 m is the distance travelled
The initial time is 10:00 pm while the arriving time is 12:30 am: this means that the time elapsed is 2.5 hours. Converting into seconds,

Therefore, the average speed for the trip is

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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:
YOUR ANSWER IS GIVEN BELOW:
Explanation:
The abundance of helium in the universe and the redshift of light from the galaxies.