1.

A train starts from rest with constant acceleration `a=1 m//s^(2)` A passenger at a distance S from the train runs at this maximum velocity of `10 m//s` to catch the train at the same moment at which the train starts. If `S=25.5` m and passenger keeps running, find the time in which he will catch the train:A. 5 secB. 4 secC. 3 secD. `2sqrt(2)` sec

Answer» Correct Answer - C
At time t, `X_(t)` and `X_(p)` are coordinates of train and passenger respectively.
`X_(t)=(1)/(2)a_(1)t^(2)` and `X_(p)=v_(P)t-S`
If passenger catches the train, ,brgt `X_(t)=X_(p)`
or `(1)/(2)a_(1)t^(2)=v_(P)t-S or t=(V_(p)-sqrt(V_(P)^(2)-2a_(1)S))/(a_(1))`
`=(10-sqrt((10)^(2)-2(1)(25.5)))/(1)=3` seconds


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