(a) steve exerts a steady force of magnitude 210n (about 47 lb.) on the stalled car in fig. 6.3 as he pushesit a distance of 18 m. the care also has a flat tire, so to make the car track straight steve must push at an angle of 30 degrees to the direction of motion. how much work does steve do? (b) refer to book.

Athin electrical heater is inserted between a long circular rod and a concentric tube with inner and outer radii of 20 and 40 mm. the rod (a) has a thermal conductivity of ka = 0.15 w/(m*k), while the tube (b) has a thermal conductivity of kb = 0.8 w/(m*k) and its outer surface is subjected to convection with a fluid of temperature t= -15°c and heat transfer coefficient 60 w/(m2 *k). the thermal contact resistance between the cylinder surfaces and the heater is negligible. (a) determine the electrical power per unit length of the cylinders (w/m) that is required to maintain the outer surface of cylinder b at 15°c. (b) what is the temperature at the center of cylinder a?