Question

Two particles are separated at a horizontal distance x as shown in figure. They are projected at the same time as shown in figure with different initial speed. The time after which the horizontal distance between the particles become zero is

• A. $u/ ⥂ 2x$
• B. $x ⥂ / ⥂ u$
• C. $2u ⥂ / ⥂ x$
• D. $u ⥂ / ⥂ x$

Answer 1

Answer: (B)

$x ⥂ / ⥂ u$

Answer 2

Let $x_{1}$and $x_{2}$are the horizontal distances travelled by particle A and B respectively in time t.

$x_{1} = \frac{u}{\sqrt{3}}.\cos 30{^\circ} \times t$ …..(i) and $x_{2} = u\cos 60^{o} \times t$

……(ii)

$x_{1} + x_{2} = \frac{u}{\sqrt{3}}.\cos 30^{o} \times t + u\cos 60^{o} \times t = ut$ ⇒ $x = ut$ $\therefore t = x/u$