North Carolina RADAR State Practice Exam

Relative motion with RADAR is defined as when:

1. Both the RADAR and object are stationary

2. Both the RADAR and object are moving in the same direction

3. The RADAR stands still while the object moves

4. Both are moving at identical speeds

The correct answer is: The RADAR stands still while the object moves

Relative motion in the context of RADAR is defined as the movement of the RADAR unit in relation to an object being tracked. When the RADAR stands still while the object moves, it provides a clear frame of reference that allows for accurate measurements of the object's speed and distance. This scenario is fundamental to how RADAR systems function; they emit a signal and analyze the return signal's time and frequency changes caused by the object's motion. In situations where both the RADAR and the object are moving, the calculation of relative speed becomes more complex, as it requires taking into account the velocities of both the RADAR and the object. If both entities are moving in the same direction or at identical speeds, the measurement could become particularly challenging, making it harder to determine the precise speed and distance of the object relative to the RADAR. This complexity is why option C, where only the object is moving relative to a stationary RADAR, is considered the clear representation of relative motion in RADAR applications.