a person walks first at a constant speed of 4.90 m/s along a straight line from point a to point b and then back along the line from b to a at a constant speed of 2.90m/s.
(a) what is her average speed over the entire trip? (in m/s)

The average speed ever the entire trip was 3.9 m/s.

Explanation:

We can calculate the average speed of the person over the full trip as:

s = (4.9 m/s + 2.9 m/s) / 2 = 3.9 m/s

To calculate the average speed we don't need what is the total displacement, but only the speed in each section of the trip (4.9 m/s and 2.9 m/s) and the number of sections of the trip (2 sections).

that tool is called an altimeter which measures your altitude which can be used to tell which atmosphere you are currently in, including the stratosphere.

hope this ! : )

causes

fossil fuels burn

cities become more industrialized

human population grows worldwide