Per NCERT Example 2.7, if the ruler dropped d = 21 cm before being caught, what is the reaction time (g = 9.8 m/s²)?
AAbout 2 s
BAbout 1 s
CAbout 0.21 s (= √(2 × 0.21/9.8))
DAbout 0.5 s
Answer & Solution
Correct answer: C. About 0.21 s (= √(2 × 0.21/9.8))
Per NCERT Example 2.7, t_r = √(2 × 0.21 / 9.8) ≈ 0.207 s ≈ 0.2 s.
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