1. The problem statement, all variables and given/known data This problem is found in The Exercises for the Feynman Lectures on Physics: A flat steel plate floating on mercury is acted upon by three forces at three corners of a square of side 0.100 m. Find a single fourth force which will hold the plate in equilibrium. Give the magnitude, direction, and point of application along the line AB. 2. Relevant equations Trig. 3. The attempt at a solution What I did to find the force vector was to imagine the forces at a centralized location then add them together. Breaking FO down into its components, I found the following: Fx=50N-35.6N=14.4N Fy=50N-35.6N=14.4N Meaning there is a net force of 20.1N at 45° from the X axis. To counteract this, the fourth force must be equal in magnitude and opposite in direction. So F4=20.1N at 225°. However, I have no idea how to figure out the point of application. I think this is related to the translation of the forces but I also had the idea of finding the moments about the center of the square due to the forces at P and Q. This yielded nothing fruitful, unfortunately. Any help would be great.