A particle P is projected with velocity u1 at an angle of 30∘ with the horizontal. Another particle Q is thrown vertically upwards with velocity u2 from a point vertically below the highest point of path of P. The necessary condition for the two particles to collide at the highest point is
Both particle collide at the highest point it means the vertical distance travelled by both the particle will be equal, i.e. the vertical component of velocity of both particle will be equal
u1 sin 30∘=u2⇒u12=u2 ∴u1=2u2