Final answer:
Only options A and B are the considered velocities. Velocity includes both magnitude and direction, thus both 12.3 m/s up and 3.8 m/s north are correct velocities. The third option, 2.2 km/sec, lacks a direction and does not satisfy the definition of velocity.
Step-by-step explanation:
The concept of velocity is fundamental in physics and refers to the rate at which an object changes its position, including both the speed and the direction of motion. Therefore, velocity is a vector quantity, which means it has both magnitude (how fast) and direction (which way).
Looking at the options provided:
- A. 12.3 m/s up - This has both magnitude (12.3 m/s) and direction (up), so it is a velocity.
- B. 3.8 m north - This also has both magnitude (3.8 m) and direction (north), qualifying as a velocity.
- C. 2.2 km/sec - This lacks a specified direction and hence is not a complete description of velocity.
- D. All of these - This choice is not correct because option C is not a velocity due to the lack of direction.
Using other examples:
- a. 3.0 m/s in the +x-direction - This is a velocity.
- b. 5.0 m/s in the +x-direction - This is also a velocity.
- c. 3.0 m/s in the -x-direction - This is a velocity as well.
- d. 5.0 m/s in the -x-direction - This, too, represents a velocity.
The correct answer to the question would be only options A and B, since they include both magnitude and direction, fulfilling the definition of velocity.