According to the meaning of the question, T=2s. When t=0, the displacement is 3.0x 10m, and it moves in the positive direction of the axis.

W=π rad/s 0.06cosθ=0.03，θ=-π/3。

x=0.06cos(πt-π/3)

Derive v=-0.06πsin(πt-π/3) and then derive a =-0.06 π 2cos (π t-π/3).

Substitute t=0.5s, s = 0.03 √ 3 = 0.052m V =-0.06π * 0.5 =-0.0942m/s A =-0.03 * π 2 * √ 3 =-0.52m/s 2.

(2) The object moves from x=-3.0x 10m to the negative direction of the OX axis.

Using the rotation vector method, the phase of this point is 2π/3 or 4π/3 (2kπ is not added here).

When the phase is 2π/3, T is the shortest, and only π-2π/3=π/3 phases are needed.

Get t & gt=(π/3)/(2π)*2= 1/3s.