To determine the magnitude of the displacement of the cyclist after 18 seconds, given that the cyclist has a constant speed of 12 meters per second, we'll use the basic formula for displacement in uniform motion:
[tex]\[ \text{Displacement} = \text{Speed} \times \text{Time} \][/tex]
Given data:
- Speed ([tex]\( v \)[/tex]) = 12 m/s
- Time ([tex]\( t \)[/tex]) = 18 s
Substitute the given values into the formula:
[tex]\[ \text{Displacement} = 12 \, \text{m/s} \times 18 \, \text{s} \][/tex]
[tex]\[ \text{Displacement} = 216 \, \text{m} \][/tex]
Thus, the magnitude of the displacement of the cyclist after 18 seconds is 216 meters.
Therefore, the correct answer is:
○ C. 216 m
