Two trains A and B, move on parallel tracks and in the same direction, with speeds vA = 20 m / s and vB = 15 m / s. Knowing that the lengths of A and B are, respectively, 60 m and 80 m, calculate how long train A takes to pass train B.

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?