Preeti walks up a stationary escalator in time t_1. On another day, standing still on the moving escalator, she reaches the top in time t_2. The time she would take walking on the moving escalator is:

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NEET Physics QUESTION #7323

Question 1

Preeti walks up a stationary escalator in time $t_1$. On another day, standing still on the moving escalator, she reaches the top in time $t_2$. The time she would take walking on the moving escalator is:

$\dfrac{t_1 t_2}{t_2-t_1}$
$\dfrac{t_1 t_2}{t_2+t_1}$✔️
$t_1 - t_2$
$\dfrac{t_1+t_2}{2}$

Correct Answer Explanation

Let escalator length $= L$. Walking speed: $v_w = \dfrac{L}{t_1}$. Escalator speed: $v_e = \dfrac{L}{t_2}$.

Combined speed: $v_w + v_e = L\cdot\dfrac{t_1+t_2}{t_1 t_2}$

Time $= \dfrac{L}{v_w+v_e} = \mathbf{\dfrac{t_1 t_2}{t_1+t_2}}$

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