1) 29.4 N
The force of gravity between two objects is given by:
where
G is the gravitational constant
M and m are the masses of the two objects
r is the separation between the centres of mass of the two objects
In this problem, we have
(mass of the Earth)
(mass of the box)
(Earth's radius, which is also the distance between the centres of mass of the two objects, since the box is located at Earth's surface)
Substituting into the equation, we find F:
2) 
Let's now calculate the ratio F/m. We have:
F = 29.4 N
m = 3.0 kg
Subsituting, we find
This is called acceleration of gravity, and it is the acceleration at which every object falls near the Earth's surface. It is indicated with the symbol 
.
We can prove that this is the acceleration of the object: in fact, according to Newton's second law,
where a is the acceleration of the object. Re-arranging,
which is exactly equal to the quantity we have calculated above.
The force that pushes charges through a wire is called voltage. Electric
current is the movement of the electrons caused by potential difference. For example,
in a circuit, the electrons in the bulb will not move without the potential
difference or voltage. When there is voltage, electric current occurs because
there is a driving force for the electrons in the wire to move.
F = ma = 1000*(23-0)/14 = 1642.86 N
When it rains, water will flow into its appropriate watershed. A ridge or topographical higher areas that connects two waters are called a divide. In the United States there is an area in the Rocky Mountain called the "continental divide." This refers to water on the east of the divide flows into the Atlantic. The water on the west side flows into the Pacific
