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Two friction disks $\backslash ($ A $\backslash )$ and $\backslash ($ B $\backslash )$ are to be brought into contact without slipping when the angular velocity of disk $\backslash ($ A $\backslash )$ is $280$ rpm counterclockwise. Disk $\backslash ($ A $\backslash )$ starts from rest at time $\backslash ($ t$=0\backslash )$ and is given a constant angular acceleration of magnitude $\backslash (\backslash$alpha $\backslash ).$ Disk $\backslash ($ B $\backslash )$ starts from rest at time $\backslash ($ t$=2\backslash$mathrm$\{$~s$\}\backslash )$ and is given a constant clockwise angular acceleration, also of magnitude $\backslash (\backslash$alpha $\backslash ).$