Question

An elevator car, whose floor to ceiling distance is equal to 2.7 m, starts ascending with constant acceleration of 1.2 ms^–2.

2 sec after the start, a bolt begins fallings from the ceiling of the car. The free fall time of the bolt is

• A. $\sqrt{0.54}s$
• B. $\sqrt{6}s$
• C. 0.7 s
• D. 1

Answer 1

Answer: (C)

0.7 s

Answer 2

$t = \sqrt{\frac{2h}{(g + a)}} = \sqrt{\frac{2 \times 2.7}{(9.8 + 1.2)}} = \sqrt{\frac{5.4}{11}} = \sqrt{0.49} = 0.7\sec$

As $u = 0$and lift is moving upward with acceleration