Answer: 
Explanation:
The equation to calculate the center of mass
of a particle system is:

In this case we can arrange for one dimension, assuming the geometric center of the Earth and the ladder are on a line, and assuming original center of mass located at the Earth's geometric center:

Where:
is the mass of the Earth
is the mass of 1 billion people
is the radius of the Earth
is the distance between the center of the Earth and the position of the people (2 m above the Earth's surface)

This is the displacement of Earth's center of mass from the original center.
Answer:
By Gaining Electrons
Explanation:
A nuetral atom is negative when it gains electrons, and it can be positive when it loses electrons.
Answer:
A. 20 N
Explanation:
weight of book is 2×10=20N
250/4= 62.5 mph
to find the mph of a car, you need to divide the number of miles traveled by the hours that it took to travel that many miles
Answer:
Take notes
Explanation:
Cuz it helps you stay on task