Coriolis Force

Another rotating platform example 另一个旋转平台示例 Another centrifugal force example 另一个离心力例子

Example: Centrifugal and Coriolis

Example: Centrifugal and Coriolis

Centrifugal Force

Whereas the centripetal force is seen as a force which must be applied by an external agent to force an object to move in a curved path, the centrifugal and coriolis forces are "effective forces" which are invoked to explain the behavior of objects from a frame of reference which is rotating.

The driver of a car on a curve is in a rotating reference frame and he could invoke a "centrifugal" force to explain why his coffee cup and the carton of eggs he has on the seat beside him tend to slide sideways. The friction of the seat or dashboard may not be sufficient to accelerate these objects in the curved path. 汽车司机在弯道上行驶时处于一个旋转的参考系中，他可以用“离心力”来解释为什么他的咖啡杯和座位旁的鸡蛋盒倾向于向侧滑动。座位或仪表盘的摩擦力可能不足以使这些物体沿曲线路径加速。 A person in a hovering helicopter above the car could describe the movement of the cup and the egg carton as just going straight while the car travels in a curved path. It is similar to the "broken string" example. 在一辆汽车上方悬停的直升机上的人，可以将杯子和鸡蛋盒的运动描述为只是直线运动，而汽车则沿着曲线路径运动。这与‘断弦’的例子类似。

The centrifugal force is a useful concept when the most convenient reference frame is one which is moving in a curved path, and therefore experiencing a centripetal acceleration. Since the car above will be experiencing a centripetal acceleration v²/r, then an object of mass m on the seat will require a force mv²/r toward the center of the circle to stay at the same spot on the seat. From the reference frame of a person in the car, there seems to be an outward centrifugal force mv²/r acting to move the mass radially outward. In practical descriptive terms, you would say that your carton of eggs is more likely to slide outward if you have a higher speed around the curve (the velocity squared factor) and more likely to slide outward if you go around a sharper curve (the inverse dependence upon r).