A 3,000-kg railway car is traveling on a level track with a velocity of 8.0 m/s to the right when it collides head-on with another railway car of mass 5,000 kg that is traveling with a velocity equal to 4.0 m/s to the left. When the two cars collide, they couple together via internal hooks that are attached to the colliding faces of each car. What is the velocity of the tandem of cars after the collision

Identify the correct relation showing that the radius r of the orbit of a moon of a given planet can be determined from the radius r of the planet, the acceleration of gravity at the surface of the planet, and the time τ required by the moon to complete one full revolution about the planet. determine the acceleration of gravity at the surface of the planet jupiter knowing that r = 71 492 km and that t= 3.551 days and r= 670.9 × 10^3 km for its moon europa.