Students are better able to understand Newton's first law when they build from their own personal experiences of bicycling, skateboarding, or riding in a car. Most have experienced a tumble when their skateboard or bicycle comes to an abrupt stop. Alternately in a car, your body continues moving when the brakes are applied and you feel the force of the seatbelt holding you in place. Start moving again and you feel your body pushed forward by the seat against your back. These common experiences provide good opportunities to learn about the concept of inertia (and to obey the law and wear seatbelts!). The state of motion of the rider does not change until an outside force is applied. We like to tell students to look at inertia as nature's way of "being lazy." This is how the name of this lab exercise, Lazy Days, is derived.