The velocity of train increases uniformly from $20\; km / h$ to $60\; km / h$ in $4\; hours$. The distance travelled by the train during this period is .......... $km$

Brakes are being applied in a car moving with speed $20\ m/s$ which produces a retardation of $5\ m/s^2$ . The distance travelled by car till it stops is........$m$

A small electric car has a maximum constant acceleration of $1\,m / s ^2$, a maximum constant deceleration of $2\,m / s ^2$ and a maximum speed of $20\,m / s$. The amount of time it would take to drive this car $1\,km$ starting from rest and finishing at rest is $.........\,s$

A train moves from rest with a uniform acceleration $a$ . Attaining a maximum speed $v$ it  starts moving with uniform retardation $a$ . Assuming $s$ = total distance covered in the  unidirectional motion of the train, its total time of journey and maximum speed are  (respectively).

A point starts moving in a straight line with a certain acceleration. At a time $t$after beginning of motion the acceleration suddenly becomes retardation of the same value. The time in which the point returns to the initial point is