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.
The normal force acts to counter the gravitational force, that is the upward direction.
Answer:
A. Kinetic energy is converted to electric potential energy, and the proton moves more slowly.
Explanation:
When a moving proton is brought close to a stationary one, the kinetic energy of the moving one is converted to electric potential and the proton moves more slowly.
Kinetic energy is the energy due to the motion of a body. A moving proton will possess this form of energy.
Two protons according to coulombs law will repel each other with an electrostatic force because they both have similar charges. This will increase their electric potential energy of both of them.
Potential energy is the energy at rest of a body. As it increases, the motion of a body will be slower and it will tend towards being stationary.
The best question that could prompt a scientific investigation is: <u>What substances dissolve in ocean water?</u>
This way the person experimenting can use several variables and make observations. Upon making observations, the person can be able to gather as much data as he can in order to answer the original question that he asked.
