Apenny is placed at the outer edge of a disk (radius = 0.179 m) that rotates about an axis perpendicular to the plane of the disk at its center. the period of the rotation is 1.60 s. find the minimum coefficient of friction necessary to allow the penny to rotate along with the disk

Asquare isothermal chip is of width w=5 mm on a side and is mounted in a substrate such that its side and back surfaces are well insulated; the front surface is exposed to the flow of a coolant at tinf=15 °c. from reliability considerations, the chip temperature must not exceed t=85 °c. if the coolant is air and the corresponding convection coefficient is h=200 w/m2 x k, what is the maximum allowable "power" of the chip? if the coolant is a liquid for which h=3000 w/m2 x k, what is the maximum allowable power of the chip?