Agirl is standing still in the middle of a baseball field. the girl catches the baseball and begins to move in the same direction as the thrown ball. what type of collision is being described?

inelastic collision

Explanation:

an elastic collision occurs when both total momentum and total kinetic energy are conserved, while during an inelastic collision only the total momentum is conserved, while the total kinetic energy is not. In particular, if two objects stick together after the collision, only the momentum is conserved, so it is an inelastic collision.

In this problem, we have a girl that catches a ball and then continues together with the ball: the two 'objects' (girl and ball) stick together after the collision, so this is an inelastic collision.