Answer:
Because there is nothing out in space , the sound waves from one astronaut's whistling can't travel over to the other astronaut's ears.
Answer:
Average velocity

Average speed,

Explanation:
(a)Average velocity
We have to find the average velocity. We know that velocity is defined as the rate of change of displacement with respect to time.
To find the average velocity we have to find the total displacement.
since displacement along east direction is 50m
and displacement along west=40m
so total displacement,

total time,

therefore, average velocity

(b)Average Speed:
Average speed is defined as the ratio of total distance to the total time
it means
Average speed= total distance/total time
here total distance,

and total time,

therefore,
Average speed,

The qualities that Galileo , Sir Isaac Newton, and Albert Einstein is that they all created models of nature. Galileo discovered Jupiter's four moons and declared that the earth revolves around the sun.Newton developed the three laws of motion, which formed the basic principles of modern physics.Albert Einstein discovered the general theory of relativity, but best known for his mass-energy equivalence formula E=mc².