Hi, 1. The problem statement, all variables and given/known data I have a question concerning fictitious forces (although its first part is irrelevant to the latter): A smooth string is extended between two points A and B in a vertically positioned circle, so that the angle between the string and the vertical axis of the circle is denoted β. A bead of mass m slides from rest down a smooth chord in a vertically positioned circle. (a) I was first asked to show that the time it would take the bead to traverse the distance AB is not dependent on the angle β. (b) I was then told that the entire set up was put in a non-inertial system, namely a cart accelerating with constant acceleration a' to the right, and was asked to find from what point A' need now the bead to be released so that the duration of slide (time required to traverse A'B') is not dependent on the length of the chord. 2. Relevant equations 3. The attempt at a solution (a) Supposing my choice of coordinate system is such that is parallel to the slide (hence, to the string): mgsin(β) = N ; mgcos(β) = ma; length of string (=L)*cos(β) = 1/2*a*t2 These three equations yielded t = sqrt(2L/g). Is that correct? (b) I realise that a fictitious force is now in action, equal to ma', whose direction is to the left. I wrote down the following equations: N = mgsin(β) + ma'cos(β); mgcos(β) - ma'sin(β) = ma Are these two correct? I am not sure how to proceed. Would appreciate some advice.