Question

Two particles separated at a horizonal distance $x$ as shown in fig. they projected at the same line as shown in fig. with different initial speeds. The time after which the horizontal distance between them become zero :

• A. $\frac{x}{u}$
• B. $\frac{u}{2x}$
• C. $\frac{2u}{x}$
• D. $noneofthese$

Answer 1

The correct option is A $\frac{x}{u}$

let the horizontal component of both particles be $\frac{u}{\sqrt{3}}cos{30}^o=\frac{u}{2}$ and $ucos{60}^o=\frac{u}{2}$ respectively

therefore let l be the distance covered by particle and l-x for particle 2 therefore

$l=\frac{u}{2}t$ and $x-l=\frac{u}{2}t$

solving above equations we get $l=\frac{x}{2}$ therefore $t=\frac{x}{u}$