Q126 / 160 · AP EAMCET 2024 (23 May Shift 1) · Physics

A person walks up a stalled escalator in 90 s . When standing on the same moving escalator he reached in 60 s . The time it would take him to walk up the moving escalator will be.

  • Correct answer
    A
    36 s
  • B
    72 s
  • C
    18 s
  • D
    27 s

Solution

$\begin{aligned} & t_1=\frac{1}{v_m}, t_2=\frac{1}{v_s} \\ & t_3=\frac{1}{v_m+v_s}=\frac{1}{\frac{1}{t_1}+\frac{1}{t_2}}=\frac{t_1 t_2}{t_1+t_2}=\frac{90 \times 60}{90+60}=36 \mathrm{~s}\end{aligned}$

Hence, the correct answer is option: 'A'.

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