Q. A ball dropped from the 9th story of a multi-storeyed building reaches the ground in 3s. In the first second of its free fall, it passes through $n$ stories, where $n$ is equal to (Take $g = 10{ms}^{- 2}$)
A) 1
B) 2
C) 3
D) 4
Explanation
(a) $9y = \frac{1}{2} \times 10 \times 3 \times 3$ or $y = 5$m
Again, $n \times 5 = \frac{1}{2} \times 10 \times 1 \times 1 = 5$ or $n = 1$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.