When a ruler falls vertically, 5 different persons catch it with different reaction times. \(\left(g=9.8 m s ^{-2}\right)\)
A. Person A has reaction time of 0.20 s.
B. Person B has reaction time of 0.22 s.
C. Person C has reaction time of 0.18 s.
D. Person D has reaction time of 0.19 s.
E. Person E has reaction time of 0.21 s.
What is the correct order of the distance travelled by the ruler for each person ?

(C) \(B>E>A>D>C\)
The distance travelled by the ruler falling freely under gravity is given by \(d=\frac{1}{2} g t^2\).
Since \(g\) is constant, the distance \(d\) is directly proportional to the square of the reaction time \(t\). Thus, a larger reaction time results in a greater distance travelled by the ruler.
The given reaction times are:
\(t_A=0.20 s\)
\(t_B=0.22 s\)
\(t_C=0.18 s\)
\(t_D=0.19 s\)
\(t_E=0.21 s\)
Arranging the reaction times in descending order:
\(0.22>0.21>0.20>0.19>0.18\)
This corresponds to:
\(t_B>t_E>t_A>t_D>t_C\)
Therefore, the correct order of the distance travelled by the ruler is:
\(B>E>A>D>C\)