$A$ car is standing $200\, m$ behind a bus,which is also at rest. The two start moving at the same instant but with different forward accelerations. The bus has an acceleration of $2\, m/s^2$ and the car has an acceleration of $4\, m/s^2$. The car will catch up with the bus after a time of:

Two stones are thrown up simultaneously with initial speeds of $u_1$ and $u_2$ $(u_2 > u_1)$. They hit the ground after $6 \, s$ and $10 \, s$ respectively. Which graph in the figure correctly represents the time variation of $\Delta x = (x_2 - x_1)$,the relative position of the second stone with respect to the first up to $t = 10 \, s$? Assume that the stones do not rebound after hitting the ground.

$A$ motor car moving at a speed of $72 \, km/h$ cannot come to a stop in less than $3.0 \, s$,while for a truck,this time interval is $5.0 \, s$. On a highway,the car is behind the truck,both moving at $72 \, km/h$. The truck gives a signal that it is going to stop in an emergency. At what distance should the car be from the truck so that it does not bump into (collide with) the truck? The human response time is $0.5 \, s$.

Two buses $A$ and $B$ are moving in opposite directions. If the first bus $A$ moves towards the east with a speed of $36 \ km/h$ and bus $B$ moves towards the west with a speed of $18 \ km/h$, then the bus $B$ appears to bus $A$ as:

Two particles start simultaneously from the same point and move along two straight lines,one with uniform velocity $v$ and the other with a uniform acceleration $a$. If $\alpha$ is the angle between the lines of motion of the two particles,then the least value of relative velocity will be at time given by

$A$ thief is running away on a straight road in a jeep moving with a speed of $9 \, m/s$. $A$ policeman chases him on a motorcycle moving at a speed of $10 \, m/s$. If the instantaneous separation between the jeep and the motorcycle is $100 \, m$,how long will it take for the policeman to catch the thief?