an athlete swims the length L of a pool in a time t1, and make the return trip to the starting position in a time t2. if they are swimming initially in the positive x-direction, determine their average velocities symbolically in (a) at the first half of the swim, (b) the second half of the swim and (c) the round trip. (d) what is their average speed for the round trip?

Asteel tube (k=50 w/mk) of inner and outer diameter di = 20mm and do=26mm, respectively, is used to transfer heat from hot gases flowing over the tube (h-hot = 200w/m2k) to cold water flowing through the tube (h-cold = 8000 w/m2k). what is the cold-side overall heat transfer coefficient uc? to enhance heat transfer 16 straight fins of rectangular profile are installed longitudinally along the outer surface of the tube. the fins are equally spaced around the circumference of the tube, each having a thickness of 2mm and a length of 15mm. what is the corresponding overall heat transfer coefficient uc? *solve for uc in both cases*