I'm not sure what you are doing with 1) and 2), but we have no information to decide if there is an angular acceleration at all. Without anything being said about it I would assume that the is zero rad/s^2. But I would check with your instructor on this.

Knowing that is zero we have that the object moves in a circle of r = 1.5 m in t = 3 s. Thus you have a constant of

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-Dan