Paper 1, Section I, A

Variational Principles
Part IB, 2015

Consider a frictionless bead on a stationary wire. The bead moves under the action of gravity acting in the negative yy-direction and the wire traces out a path y(x)y(x), connecting points (x,y)=(0,0)(x, y)=(0,0) and (1,0)(1,0). Using a first integral of the Euler-Lagrange equations, find the choice of y(x)y(x) which gives the shortest travel time, starting from rest. You may give your solution for yy and xx separately, in parametric form.