Problem

Two identical balls, each of mass m, are connected by a string of negligible mass and leng...

Two identical balls, each of mass m, are connected by a string of negligible mass and length 2l. A short string is attached to the middle of the string connecting the two balls and is pulled vertically with a constant force P. If the system starts from rest at θ = θ0and assuming that the balls only move in the horizontal direction, determine the expression for the speed of the two balls as θ approaches 90°. Neglect the size of the balls as well as friction between the balls and the surface on which they slide.