Two particles are separated at a horizontal distance `x` as shown in (Fig. 5.57). They are projected at the same time as shown in the figure with different initial speed. Find the time after which the horizontal distance between the particles becomes zero.
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Explanation

Let `x_1 and x_2` are the horizontal distances travelled by particle `A and B`, respectively, in time `t`.
`x_1 = (u)/(sqrt(3)). Cos 30^2 xx t` ….(i)
and `x_2 = u cos 60^@ xx t` …(ii)
`x_1 + x_2 = (u)/(sqrt(3)). Cos 30^@ xx t + u cos 60^@ xx t = ut`
`rArr x = ut rArr t = x//u`.