Two Masses Hung From a Spring Scale: A Simple Textbook Problem we Keep Getting Wrong

This is a classic application of Newton s Laws. It makes a great demonstration of static force, equilibrium and Net Force. Two masses are hung from opposite sides of a pulley. In between is a spring scale. What is the force reading on the scale Most people will report the answer to this physics problem wrong the first time through, thats ok, it s called learning This demonstration often comes up in introductory physics courses including AP Physics