Correct answer: a = 10 m/s²
The net acceleration of a particle at the periphery of the disc is the vector sum of the tangential acceleration and the centripetal acceleration. Tangential acceleration is given by a_t = αR = (2.0)(0.5) = 1 m/s². Angular velocity after 2 seconds is ω = αt = (2.0)(2) = 4 rad/s. Centripetal acceleration is a_c = ω²R = (4²)(0.5) = 8 m/s². Net acceleration is a = √(a_t² + a_c²) = √(1² + 8²) = √65 ≈ 10 m/s².