Originally Posted by **idol** 1:why velocity is relative but acceleration is absolute .
2:what do we mean by the term "absolute" in kinematics?
3:can we find centripetal and centrifugal force simultaneously in non inertial frame of reference ? |

1: SR takes the speed of light to be a constant, as implied by the Lorentz transformation. Under this rule we get the velocity transformation laws. Accelerating frames are not a feature of the Lorentz transformations so the law is that v < c, but you can have any value for the acceleration. There is a distinction here with General Relativity: accelerating frames are now allowed but they too have their "distortions." There is still no upper limit on the acceleration but accelerations now look different in different reference frames.

2: I'm not sure what you mean by "absolute" either. Do you have an example you can share?

3: Centripetal force is defined as the radial force an object undergoes as a result of its speed in an arc. (Typically we have objects moving in a circular orbit and constant speed which gives a constant centripetal acceleration, but if the object is not on a circular path we still define aC = mv^2/r, it's just that we no longer have a constant v and r.) The centrifugal force is similar to the centripetal force, just that it is in the opposite direction. The distinction is that centripetal force is calculated as mv^2/r and that the centrifugal force is due to an object's inertia.

-Dan