Two runners are observed from the ground. Runner 1 has a mass of 60kg and runs due north at 5.0ms−1; Runner 2 has a mass of 80kg and runs due east at 4.0ms−1.
a. Determine the total translational kinetic energy of the two-runner system as measured by the ground observer.
b. An observer runs alongside Runner 1 at the same speed and in the same direction as Runner 1. Relative to this moving observer, what are the kinetic energies of Runner 1 and Runner 2?