In circular motion, why don’t centripetal and centrifugal forces cancel each other? Well, they don’t cancel each other because they are not present simultaneously for the same observer. Only one is present at a time for one observer. If you take ground observer – inertial observer to be more precise – then only centripetal force is applicable and of course it is applicable towards the centre. There is no centrifugal force present here. Since both are not present simultaneously, they don’t cancel each other. In case of non-inertial or accelerated observer, only centrifugal force is present – it acts away from the centre. There is no centripetal force applicable. Since both are not present simultaneously, they can’t cancel each other.