Question 57: Motion in 1D

Question

A boy reaches the airport and finds that the escalator is not working. He walks up the stationary escalator in time t
1
. If he remains stationary on a moving escalator then the escalator takes him up in time t
2
. The time taken by him to walk up on the moving escalator will be :

Accepted Answer

L = Length of escalator
$${V_{b/esc}} = {L \over {{t_1}}}$$
When only escalator is moving.
$${V_{esc}} = {L \over {{t_2}}}$$
when both are moving
$${V_{b/g}} = {V_{b/esc}} + {V_{esc}}$$
$${V_{b/g}} = {L \over {{t_1}}} + {L \over {{t_2}}} \Rightarrow \left[ {t = {L \over {{V_{b/g}}}} = {{{t_1}{t_2}} \over {{t_1} + {t_2}}}} \right]$$

Answer

$${{{t_1}{t_2}} \over {{t_2} - {t_1}}}$$

Answer

$${{{t_1} + {t_2}} \over 2}$$

Answer

$${{{t_1}{t_2}} \over {{t_2} + {t_1}}}$$

Answer

$${t_2} - {t_1}$$

Motion in 1D

A boy reaches the airport and finds that the escalator is not working. He walks up the stationary escalator in time t 1 . If he remains stationary on a moving escalator then the escalator takes him up in time t 2 . The time taken by him to walk up on the moving escalator will be :

Choose the correct answer: