what is centrifugal reaction?

Answer 1

I assume you are referring to an apparent centrifugal reaction force. That is an outward directed force that you feel on your body when you are moving in a circular path; it is the force that seems to make your body heavier when you are "pulling G's" in an aerobatic plane or on a roller coaster.

It is a compelling illusion, but in fact the only force is centripetal, that is a force directed to the centre of the circular path which is causing your motion to be circular rather than a straight line. The centrifugal reaction force is the embodiment of Newton's second law (I believe) that states that any force (or 'action') causes an apparent reaction force which is equal in magnitude but opposite in direction. Hence the centripetal, centre-directed force causes an apparent centrifugal outward directed force which you can feel.

Answer 2

poorcocob..... is absolutely correct. But perhaps you'd like to know why centripetal force is there for centrifugal force to react to.

One of Newton's several laws (he was a busy man back then) specifies that a body at rest will remain at rest or a body in motion will stay moving in a straight line until some force causes that to change. When a body is revolving around something, like a rock swinging around on a string or the Earth revolving around the Sun, the string or gravity keeps tugging at the rock or the Earth to change the direction of the rock or Earth, which want to travel in a straight line according to Newton's law.

That change of direction as the rock or Earth go around the center of the revolution is caused by centripetal force...the force pulling the rock or Earth towards the center of revolution. C = m (v(t)/r^2) is the equation for centripetal force; where m is the mass of the body (stone or Earth), v(t) is the tangential velocity in the direction of that attempted straight line, and r is the distance between the center of revolution and the body revolving around it.

The tangential velocity (v(t)) keeps changing direction rather than speeding off in a straight line; so a force is clearly acting on the rock or the Earth. That's the centripetal force.

As a result of the string or Sun tugging on their respective bodies and continually changing their direction of motion, there is, according Newton once again, an equal and opposite force tugging outward, away from the center of revolution. If there were no equal and opposite force, the centrifugal force, the rock would fall into the center of revolution and the Earth would fall into the Sun.