OnlineCBT
Physics · MOTION IN A STRAIGHT LINE
हिन्दीTo measure reaction time, a student's friend drops a ruler vertically from rest between the student's fingers. The student catches the ruler after it travels a distance of \( 19.6\text{ cm} \). Taking \( g = 9.8\text{ m/s}^2 \), the reaction time of the student is:
Correct answer · Option 1
\( 0.2\text{ s} \)
Explanation
Formula \( d = \frac{1}{2} g t_r^2 \implies t_r = \sqrt{\frac{2d}{g}} \). Here \( d = 0.196\text{ m} \), \( g = 9.8\text{ m/s}^2 \). So \( t_r = \sqrt{\frac{2 \times 0.196}{9.8}} = \sqrt{0.04} = 0.2\text{ s} \).
