Final answer:
Option 2, '30 meters per second going down,' is the correct answer since it includes both magnitude and direction, effectively representing a velocity. Speed alone is not sufficient to describe velocity without the directional component.
Step-by-step explanation:
The student asked which option represents a velocity. By definition, velocity is a vector quantity, meaning it has both magnitude and direction. It is defined as the rate at which an object changes its position. Option 1, '30 meters per second,' describes a speed since it lacks a direction. However, option 2, '30 meters per second going down,' clearly indicates not only the speed but also a specific direction ('going down'). Therefore, '30 meters per second going down' is the correct answer because it includes both magnitude and direction, making it a velocity.
To illustrate with an example, suppose an airplane passenger moves -4 meters in 5 seconds (towards the back of the plane). Their average velocity would be -4 meters divided by 5 seconds, resulting in -0.8 m/s, which includes the direction indicated by the negative sign. Another example is when an object falls and we discuss its velocity; it is both the speed at which it falls and the direction towards the ground. The SI unit for velocity is meters per second (m/s), but it can also be represented in other units such as kilometers per hour (km/h).