A small object attached to a thread is being swung around counterclockwise in a circle of radius R_o with uniform angular acceleration α. The position vector r of the object is given by: r̄ = î R_o cos Φ + ĵ R_o sin Φ where Φ = ω_it + (1/2)αt², here ω_i denotes the initial angular velocity and t is the time elapsed. Given that the mass of the object is m, and its moment of inertia is I, find its tangential acceleration a_t, and using τ̅ = Iα̅, find the torque acting on it.

• A. $a_t=0$, $\tau =0$
• B. $a_t=0$, $\tau = m (R_0)^2 \alpha \hat{k}$
• C. $a_t=R_0\alpha$, $\tau = m (R_0)^2 \alpha \hat{k}$
• D. $a_t=R_0\alpha$, $\tau =0$