Jim Newstrom, age 13, of Omaha, Nebraska, for his question:
What is centrifugal force?
This topic takes us into the realm of dynamics the complex laws of force and motion. In a general way, we know about some of these forces from everyday experience. For example, the force of gravity holds us onto the globe controlling our every motion. To this extent, physicists agree with this common experience. The general public has a few ideas about centrifugal force. But in this case, the experts do not agree with our popular notions.
The term centrifugal force suggests circular motion. Most people suspect it works to pull revolving objects toward the center of their orbital circles. Physicists, however, insist that this is not true at all. Actually centrifugal means to move away from the center. Obviously this is the wrong direction to fit the popular notion the correct term being centripetal meaning to seek the center. Centripetal force exerts itself on objects moving in a curved path. In exerting its movement toward the center, it bends their curved paths around in circular orbits.
The motions of planets and stars are governed by an assortment of cosmic forces including gravity and centripetal force. These forces act on every particle of matter in the universe in precise ratios and at all times. Sometimes the force of gravity may be pulling a moving object in one direction while centripetal force is pulling it in another direction somewhat like a tug of war.
When the tug of war teams are evenly balanced, the moving object is held in a fixed pattern. Planets moving along their curved paths are kept in place by a balance of centripetal force and the gravitational attraction between themselves and the sun. This delicate balance involves a number of factors including mass or weight, speed, and the size of the circle determined by the curved orbit. If any factor in this precise ratio is unbalanced, the tug of war becomes one sided. Then other dynamic forces enter the picture. Suppose, for example, no cosmic forces at all were exerted on a moving body. (This could not really happen, at least not in the universe as we know it). But in theory, that force free moving object would start off at a certain speed in a certain direction and keep on going at the same speed in the same direction.
This is where the concept of centrifugal force enters the picture. V1hen you swirl around a ball on a string, centripetal force is exerted to pull its curved path in toward the center. If you let go, it uses the energy of its motion to break free and go off in another direction. Something we call centrifugal force seems to swirl it outward from the center of its former orbit. Actually, it takes a new path because centripetal force loses its grip. Centrifugal force is a sort of ghostly pattern that enters the picture when the ratios involved in centripetal force are changed.
The sun exerts an enormous gravitational pull that reaches to the limit of the Solar System and beyond dwindling with distance. The exertion of centripetal force bends the curved path of a planet in orbit. Its orbital pattern is determined by its mass or weight, its speed and its distance from the sun. If this ratio were upset, gravity might pull it into the sun. Or what we call centrifugal force might allow it to zoom on out of the Solar System.