Two carts of varying mass roll without slipping on wheels with negligible rotational inertia. The carts are connected to each other and to walls by springs of varying stiffness (numbered from left to right). Initially the cart on the left (mass 1) is at its natural resting position and the one on the right (mass 2) is held one unit to the right of its natural resting position and then released. This Demonstration shows the motion of the carts.