Answer:
30 metres.
Step-by-step explanation:
Given that a red ball moves horizontally in a 30 m long tube.
Displacement is the distance travelled in a specific direction. It has both magnitude and direction.
Since the motion is horizontal, it moves is a certain direction.
Within the stipulation of time, the displacement will be the distance covered in the horizontal direction which is 30 metres.
Therefore, the displacement of the motion of the red ball is 30 metres.