Answer:
The average speed for the entire run is 12 km/h.
Explanation:
The average speed is given by the following equation:

Where:
: is the total distance
: is the total time
If during the first hour, they ran a total of 13 kilometers and then, they ran 5.0 kilometers during the next half an hour we have:


Hence, the average speed is:

Therefore, the average speed for the entire run is 12 km/h.
I hope it helps you!
Answer:
calculated the speed of light over a short distance
Explanation:
Albert Michelson <u>was an American physicist who conducted an experiment regarding the speed of light in the air 1880s.</u> He believed in the existence of "aether," a field of space that is deemed necessary for transporting electromagnetic forces. In order to do this, he setup a device in order to accurately measure the speed of light in in aether. His device is now known as <u>"Michelson interferometer." </u><em>The result was actually negative. </em>
In order to make his experiment even more accurate, he collaborated with Edward Morley, a famous American scientist. Although the result failed, together, they were able to improve and come with the a standard length of light. This calculated the speed of light over a short distance, which was the significant result of Michelson's experiment.
Thus, this explains the answer.
Water that is pure, will always freeze at 0 degrees.
D. a train on a straight track
This is an open series circuit