Final answer:
Using the conservation of momentum for an elastic collision, the velocity of object B after colliding with object A is found to be 5.0 m/s in the +x-direction.
Step-by-step explanation:
The question involves the concept of an elastic collision between two objects of equal mass in one dimension. In an elastic collision, both momentum and kinetic energy are conserved. When object A, moving at 5.0 m/s in the +x-direction, collides with object B, moving at 3.0 m/s in the -x-direction, and afterwards object A is moving at 3.0 m/s in the -x-direction, the velocity of object B can be determined using conservation of momentum.
Since both masses are equal and we take the initial velocity of A as positive and that of B as negative due to their directions, we can set up the equation: (5.0 m/s) + (-3.0 m/s) = (-3.0 m/s) + velocity of B after collision. Solving for the unknown gives us a velocity of object B after the collision as 5.0 m/s in the +x-direction.