A uniform disk with mass $40\mathrm{.}0$ kg and radius $0\mathrm{.}200$ m is pivoted at its center about a horizontal, frictionless axle that is stationary. The disk is initially at rest, and then a constant force F$=30\mathrm{.}0$ N is applied tangent to the rim of the disk. a$.$ What is the magnitude v of the tangential velocity of a point on the rim of the disk after the disk has turned through $0\mathrm{.}400$ revolution?b$.$ What is the magnitude a of the resultant acceleration of a point on the rim of the disk after the disk has turned through $0\mathrm{.}400$ revolution?