# Mechanism of Mechanics.

A $$3$$ Kg uniform rod rotates in a vertical plane about a smooth pivot at $$B$$. A spring of constant $$K=300$$ N/m and of unstretched length $$100$$ mm is attached to The rod as shown .Knowing that in the position shown the rod has an angular velocity of $$4$$ rad/s clockwise,determine the angular velocity of The rod after it has rotated through $$90^°$$.

Take $$g=10$$ m/s^2

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