To analyze the student's motion, we need to consider the definitions of speed, velocity, and how they relate to each other.
- Speed is a scalar quantity and measures how fast an object is moving, regardless of its direction.
- Velocity is a vector quantity that includes both speed and direction.
In this case, the student first walks east at a speed of 100 meters in 2 minutes, which is a constant speed. Then, she walks north at a speed of 200 meters in 4 minutes, which is also a constant speed.
However, while her speed remains constant in each segment of her walk, her velocity changes because her direction changes (from east to north).
Therefore, the correct statement is:
Her velocity changes because her direction changes.