$A$ 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 particles $A$ and $B$ are moving along a straight line with $B$ ahead of $A$. If their velocities remain constant,what will be the effect on the magnitude of their relative velocity when $A$ is ahead of $B$?

Two trains,one of length $100 \, m$ and another of length $125 \, m$,are moving in mutually opposite directions along parallel lines. They meet each other,each with a speed of $10 \, m/s$. If their accelerations are $0.3 \, m/s^2$ and $0.2 \, m/s^2$ respectively,then the time they take to pass each other will be ......... $s$.

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:

The distance between two particles is decreasing at the rate of $6 \,m/s$. If these particles travel with the same speeds and in the same direction,then the separation increases at the rate of $4 \,m/s$. The speeds of the particles are:

Two skaters $P$ and $Q$ are skating towards each other. Skater $P$ throws a ball towards $Q$ every $5 \,s$ such that it always leaves her hand with speed $2 \,ms^{-1}$ with respect to the ground. Consider two cases:
$(I)$ $P$ runs with speed $1 \,ms^{-1}$ towards $Q$,while $Q$ remains stationary.
$(II)$ $Q$ runs with speed $1 \,ms^{-1}$ towards $P$,while $P$ remains stationary.
Note that irrespective of the speed of $P$,the ball always leaves $P$'s hand with speed $2 \,ms^{-1}$ with respect to the ground. Ignore gravity. At what intervals will the balls be received by $Q$?