A small block B fit inside a slot cut in arm OA which rotates in a vertical plane at a con...

A small block B fit inside a slot cut in arm OA which rotates in a vertical plane at a constant rate. The block remains in contact with the end of the slot closest to A and its speed is 4.2 ft/s for 0≤ θ ≤ 150º. Knowing that the block begins to slide when θ = 150º, determine the coefficient of static friction between the block and the slot.