Final answer:
The sum of two velocity vectors requires accounting for both magnitude and direction. Without the direction of the second vector, it's impossible to give a definitive answer. If both vectors were along the x-axis, their sum would be 7.0 m/s in the same direction.
Step-by-step explanation:
The question asks for the sum of two velocity vectors. When adding velocities, which are vector quantities, you must account for both magnitude and direction. The velocity vector v1 is directed along the x-axis with a magnitude of 4.0 m/s, which we can represent as (4.0, 0) in x and y components. The velocity vector v2 has a magnitude of 3.0 m/s, but its direction is not specified in the question, so it is impossible to find the resultant vector without more information.
If v2 were also along the x-axis, the sum would be simple: you would just add the magnitudes to get 7.0 m/s along the x-axis. However, if v2 is in any other direction, you would need to know that direction to calculate the correct resultant vector using vector addition rules.