The magnitude of the tidal force between the International Space Station (ISS) and a nearby astronaut on a spacewalk is approxim
ately 2GmMa/r3 . In this expression, M is the mass of the Earth, r=6.79×106m is the distance from the center of the Earth to the orbit of the ISS, m=135kg is the mass of the astronaut, and a=13m is the distance from the astronaut to the center of mass of the ISS. Calculate the magnitude of the tidal force for this astronaut. This force tends to separate the astronaut from the ISS if the astronaut is located along the line that connects the center of the Earth with the center of mass of the ISS.