Question

the greatest acceleration or deceleration that a train may have is a.The minimum time in which the train can start from one station to stop at the next is
a. 2sqrt{s/a}
b. sqrt{s/a}

Answer 1

As in the figure, for the train to take minimum time, it should accelerate with it's max acceleration for half the duration and decelerate for the next half.
$$s = \frac12 t v_{max} = \frac12 t(\frac{at}{2}) $$
It gives $$ t= 2\sqrt{\frac sa}$$

Answer 2

tnx a lot.. :)

Answer 3

also try the v-t (velocity - time) graph method...in complex cases it is really useful...and more easy to understand.just have to keep 2 things in mind:
1)equate the slope of graph to acceleration.
2)equate the area under graph to total displacement....

Answer 4

thank u.. :)