The 0.75-kg particle is attached to the light slender rod OA which pivots freely about a...

The 0.75-kg particle is attached to the light slender rod OA which pivots freely about a horizontal axis through point O. The system is released from rest while in the position θ = 0 where the spring is unstretched. If the particle is observed to stop momentarily in the position θ = 50°, determine the spring constant k. For your computed value of k, what is the particle speed v at the position θ = 25°?