OK I have had no problem getting the correct answers but my understanding is a bit unclear. Part a) Mass on a turntable at point of slipping. Given rpm and radius from centre find coeffcient of friction. No problem just assume frictional force is equaly to the force causing the acceleration towards the center ie mrw^2 _ I got this OK But then the turntable is slowed down. Find the resultant force of the object. The answer is mrw^2 (and I undersatnd that this force must exist and must be directly towards the centre because it causes the accelration and prevents motion in a straight line) My dilema is what has happened to the friction? It must still exist and my first idea was that it needed to be subtracted from mrw^2 to find the resultnat force. I think this is wrong but am still not sure why?