1. The problem statement, all variables and given/known data What is an inertial frame of reference? 2. Relevant equations -A particle at rest or moving at a constant velocity in an inertial frame of reference implies that the sum of the forces acting on the particle is zero -The tendency of a body to keep moving once it is set in motion results from a property called inertia. 3. The attempt at a solution My best guess is that it is a location in space where internal or external forces are not acting on it.