Heidi T. answered • 01/30/22
Experienced tutor/teacher/scientist
It is because of inertia (inertia = the resistance of a body to a change in motion). The centrifugal force does not exist, it is used only in physics problems to "balance" the forces, basically providing a way to represent the inertia of the problem.
So here is what's happening: The Earth is moving through space at some velocity, v. Left to itself, it will continue to travel at this velocity in a straight line forever. However, the Sun is in the picture and it is exerting a gravitational force on the Earth. If the Earth was stationary in space (or relative to the Sun), the force of gravity due to the Sun would pull the Earth in, along the straight line between them. But the Earth is not stationary, it is moving. So the gravitational force of the Sun causes the path of the Earth to change, just enough to keep the Earth going around the Sun. If the Earth slowed down, it would spiral into the Sun. If the Sun exerted less of a gravitational force, the Earth would turn toward the Sun, but eventually its inertia would be greater than the force due to the Sun's gravity (because the Earth is getting farther from the Sun). At this point, the Earth would continue on its way in a straight line through the Universe, until the next force acted on it.
Heidi T.
Also from Wikipedia: "In Newtonian mechanics, the centrifugal force is an inertial force (also called a "fictitious" or "pseudo" force) that appears to act on all objects when viewed in a rotating frame of reference. It is directed away from an axis which is parallel to the axis of rotation and passing through the coordinate system's origin. If the axis of rotation passes through the coordinate system's origin, the centrifugal force is directed radially outwards from that axis." The centrifugal force (represented in equations as (M v^2)/r ) isn't really there. It describes the inertia (resistance to change in motion) of the orbiting object. If the Sun were to suddenly have 0 mass, the Earth would not fly directly away from the Sun, which would be required if the centrifugal force were a real force, such as the gravitational force. Without the Sun to cause the earth's velocity vector to change direction, the Earth would move on a trajectory that is tangent to the orbit in a straight line, as required by Newton's First Law. If the Earth were not moving, then the only force acting would be the gravitational force of the Sun, and the Earth would fall into the Sun in a straight line from its original position to the Sun. The comparison of the Earth's orbit with its rotation doesn't make much sense. Yes, the earth spins on its axis because there is no (significant) force slowing it down. That really has nothing to do with why the Earth stays in orbit even though the only force causing the rotation is the gravitational force of the Sun.01/31/22
0825 2.
👍🏻02/01/22
0825 2.
but, according to a page in Wikipedia, it said- The Earth does not roll directly towards the Sun because it is moving too fast. The force pulling the Earth towards the sun is about the same as a second force. This second force is called the centrifugal force. The centrifugal force exists because the Earth moves sideways. This sideways motion makes the distance between the Earth and Sun increase. Why does the Earth not fall into the Sun? The answer is simple but very important. The speed of the Earth's movement creates a centrifugal force which balances the gravitational force between the Sun and the Earth. Why does the Earth continue spinning? Because there is no force to stop it.01/31/22