A particle is launched with a horizontal velocity v0 = 0.55 m/s from the position shown...

A particle is launched with a horizontal velocity v₀ = 0.55 m/s from the position shown and then slides without friction along the funnel-like surface. Determine the angle θ which its velocity vector makes with the horizontal as the particle passes level O-O. The value of r is 0.9 m.