Then, to determine the inertia of another object, which we will label with the subscript 1, just arrange a one-dimensional collision between object 1 and the standard, under the right conditions (basi...Then, to determine the inertia of another object, which we will label with the subscript 1, just arrange a one-dimensional collision between object 1 and the standard, under the right conditions (basically, no net external forces), measure the velocity changes Δv1 and Δvs, and take the quantity −Δvs/Δv1 as the numerical value of the ratio of the inertia of object 1 to the inertia of the standard object.