CAN WE USE CENTRIFUGAL FORCE TO EXPLAIN CIRCULAR MOTION?
extracted from HENIEMANN ADVANCED SCIENCE - PHYSICS by PATRICK FULLICK
Many people believe that circular motion involves centrifugal force – that is, a force which acts radially outwards from the centre of the circle, in exactly the opposite direction to centripetal force. Why is this?
The careful analysis of circular motion clearly shows that an object moving in a circle accelerates towards the centre of the circle, and as a direct consequence of Newton’s second law of motion, a centripetal force must be the cause of this acceleration.
The illusion of centrifugal force comes from our own experience of circular motion, for example in a car or on a fairground ride as in the figure shown, when instead of viewing the situation from the outside (a frame of constant velocity) we view it from within the system itself (a rotating frame of reference).
This illusion comes about by direct
analogy with our own experience of weight. We know that the Earth is pulling
down on us as we stand on its surface because
we experience an upward push of the Earth’s surface on our feet. In the
same way, as we experience the inward push of the seat we rotate on a fairground
ride, we believe that this must be due to centrifugal force pushing us outwards
against the seat. This is another example of the principle of equivalence,
the idea that gravity and acceleration are equivalent, since the rotating fairground
ride is a frame of reference which is constantly accelerating.