This simulation includes a wheeled cart on a horizontal surface that is tied to a mass with a string that passes over a pulley. The mass hangs over the edge of the table, and when the cart is released the mass accelerates down towards the ground. The learner can vary the mass of the cart and the mass of the hanging mass. The data that the simulation provides as the cart rolls and the mass falls include a motion diagram that visually shows the rate of acceleration of the cart, a motion diagram of the falling mass, and numeric results for the tension in each rope, the time elapsed, and the displacement of the objects. There is accompanying informative text in the Related Resources section that explains how to solve two body problems using Newton’s second law. This text provides solved examples as well as additional practice.