16.53. Set Up: For a heat engine For a Carnot engine Gravitational potential energy is Solve: (a) This engine has a very low thermal efficiency. (b) This equals the work output of the engine. so (c) Since 80% of food energy goes into heat, you must eat food with a food energy of Each candy bar gives The number of candy bars required is 16.54. Set Up: Solve: (a) For For must be increased (b) must be decreased 16.55. Set Up: The sun radiates heat energy at a rate The rate at which the sun absorbs heat from the surrounding space is negligible, since space is so much colder. This heat flows out of the sun at 5800 K and into the surrounding space at 3 K. From Appendix F, the radius of the sun is The surface area of a sphere with radius R is Solve: (a) In 1 s the quantity of heat radiated by the sun is (b) The process of radiation is irreversible; this heat flows from the hot object (sun) to the cold object (space) and not in the reverse direction. This is consistent with the answer to part (a). We found
This is the end of the preview. Sign up
access the rest of the document.