Water is heated by submerging 50-mm-diameter, thin-walled copper tubes in a tank and passing hot combustion gases ( 750 k) through the tubes. to enhance heat transfer to the water, four straight fins of uniform cross section, which form a cross, are inserted in each tube. the fins are 5 mm thick and are also made of copper ( 400 w/m·k).

Abird flies directly overhead from where you stand at an altitude of 300.0 m and at a speed horizontal to the ground of 20.0 m/s. the bird has a mass of 2.0 kg. the radius vector to the bird makes an angle \thetaθ with respect to the ground. the radius vector to the bird and its momentum vector lie in the xyxy-plane. what is the bird’s angular momentum about the point where you are standing?