Two bodies start moving from the same point along a straight line with velocities $v_1 = 6 \, m/s$ and $v_2 = 10 \, m/s$,simultaneously. After what time will their separation become $40 \, m$?

$A$ train is moving at a constant speed $V$. When its driver observes another train in front of him on the same track and moving in the same direction with constant speed $u$. If the distance between the trains is $x$,what should be the minimum retardation of the train to avoid a collision?

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 time at which the relative velocity is minimum is given by:

$A$ person sitting in a moving train with his face towards the engine,throws a coin vertically upwards. The coin falls ahead of the person. The train:

Two trains $A$ and $B$,initially $120\, km$ apart,start moving towards each other on the same track with a velocity of $60\, km/hr$ each. At the moment of start,train $A$ blows a whistle,which reflects off train $B$ and subsequently reflects off train $A$,and so on. If the velocity of sound waves in air is $1200\, km/hr$,what is the total distance travelled by the sound waves before the trains crash (in $km$)?

$A$ particle is dropped from rest and another particle is thrown downward simultaneously with initial speed $u$. Then: