hurricanes in the northern hemisphere to rotate in the counterclockwise direction, while in the southern hemisphere, they rotate in a clockwise direction.
NEWTON’S LAW OF GRAVITATION Gravitational force affects all things on or near the earth, including the Moon, which is a distance away from the earth. The force of gravity supplies the necessary centripetal force to allow for the rotation of the moon. These are the identical forces that cause the earth to rotate around the sun and for galaxies to rotate around a specific point. You should know that it is the weakest of the four basic forces found in nature (such as electromagnetic forces, weak nuclear forces, and strong nuclear forces). Unlike other forces, it is always attractive. It is along a line that joins the centers of mass of two objects. Figure 27 shows gravitational forces:
Figure 27.
The magnitude of force is equal in each direction, regardless of the mass of the object because of Newton’s third law. If the forces were different, the moon would leave the earth’s orbit or would crash into the earth. The center of mass is used in equations regarding this because these bodies tend to be quite large. This brings us to Newton’s Universal Laws of Gravitation, which states that force equals the gravitational constant multiplied by the value of both masses, divided by the radius (the distance between the two masses) squared. Figure 28 shows this equation:
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