\[(a)\;0.8 s\quad (b)\;0.7 s \quad (c)\;0.6s \quad (d)\;0.5 s\]

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Considering elevator at rest the relative acceleration of bolt is

$a_r=9.8+1.2=11m/s^2$

Now after 2 seconds after the car starts moving with acceleration $1.2 m/s^2$ its velocity will be

$v_{\large car}$$=at=(1.2) \times 2=2.4 m/s$

But w.r.t elevator the bolt has zero velocity , and acceleration $=11 m/s^2$

Therefore $t=\sqrt {\large\frac {2s}{a}}$

$\qquad\qquad=\sqrt {\large\frac{2 \times 2.7}{11}}$$=0.7 s$

Hence b is the correct answer

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