A computer hard disk 8.0 cm in diameter is initially at rest. A small dot is painted on the edge of the disk. The disk accelerates at 680rad/s2 for 12s, then coasts at a steady angular velocity for another 12s. What is the speed of the dot at t = 1.0 s?

Explanation:

According to the kinematic equation,

And, we are given

        = 0,      a = 680

        t = 12 sec

Putting the given values into the above formula as follows.

                    =

                    = 8160 rad/s

Also, we know that

                       =

                       = 326.4 m/s

Thus, we can conclude that the speed of the dot at t = 1.0 sec is 326.4 m/s.

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