Fact or Fiction?
Centrifugal force has been called a “fictitious force”, one that does not really exist. So just what is happening when you drive your car around a bend in the road, and you feel yourself thrown outward against the door?
Imagine a ball with a string attached, and you grasp the string and twirl the ball in a circle. Perhaps there really is a “centrifugal force” which pushes away from the center of the circle, keeping the ball out there. This is depicted in Figure 1:
Now suppose you were to let go of the string when the ball reached point A. The forward motion of the ball would hurl it to the left, while the centrifugal force would simultaneously hurl it upwards. The resulting trajectory is depicted in Figure 2:
However if you were to perform this experiment, you would discover something entirely different as illustrated in Figure 3:
The ball flies off on a tangent to the circle, hurling to the left but with no upward component. There is no indication of any “centrifugal force” which pushes away from the center of the circle.
OK, so maybe there IS no centrifugal force. But you may ask “why am I getting pushed against the car door as I round a bend in the road?” The simple answer is that you are not being pushed against the door, the door is pushing against you!
Now look at Figure 4:
Imagine you are the ball, and you are sitting in a car as shown. As the car rounds the turn, your body prefers to go in a straight line as depicted. The car, however, continues around the turn. In effect the car pushes against your body, forcing you around the turn. If feels as if you are being pushed against the door, but the door is really pushing on you! There is no string tied to your body to force you in a circular path (as with the ball). It is the car pushing against your body that forces you around the circle.
Gee, why was this so tricky? In order to properly evaluate the forces at work, this kind of scenario must be viewed from the outside. If you are inside (sitting in the car), you have the wrong frame of reference, and there indeed appears to be a “centrifugal force” at work. And it feels very real too!
So tell me, is there a centrifugal force or not? Well, it’s all relative to your frame of reference, now isn’t it?! (Einstein’s theory of relativity and all…)
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