Verified Solution • 2025–26 Session moderate

QNEET-2017-Ph-989: NEET 2017 Physics - Class 11 NEET-2017-Ph-989 Solution: Preeti reached the metro station and found that the escalator…

Preeti reached the metro station and found that the escalator was not working. She walked up the sationary escalator in time

t_1

. On another days if she remains stationary on the the moving escalator then the escalator takes her up in time

t_2

. The time taken by her to walk up on the moving escalator will be

\frac{t_1t_2}{t_2-t_1}

\frac{t_1t_2}{t_2+t_1}

t_1-t_2

\frac{t_1+t_2}{2}

Multiple Choice Options

A ${{{t_1}{t_2}} \over {{t_2} - {t_1}}}$ t 2 _ _ t 1 _ t 1 _ t 2 _ _
B ${{{t_1}{t_2}} \over {{t_2} + {t_1}}}$ t 2 _ + t 1 _ t 1 _ t 2 _ _
C ${{t_1} - {t_2}}$ t 1 _ _ t 2 _
D ${{{t_1} + {t_2}} \over 2}$ 2 t 1 _ + t 2 _ _

Step-by-Step Verified Solution

Velocity of preeti with respect to elevator v 1 = d t 1 Velocity of elevator with respect to ground v 2 = d t 2 _ Net velocity of preeti on moving escalator with respect to the ground v = v 1 + v 2 d t = d t 1 + d t 2 1 t = 1 t 1 + 1 t 2 _ t = t 1 t 2 t 1 + t 2 Here t is the time taken by preeti to walk up on the moving escalator.

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