The two objects in the drawing are made from the same material (emissivity = 0.500) and have a temperature of 323 K. One is a cube of edge length ro = 0.280 m, and the other is a sphere of radius ro. They are placed in a room whose temperature is 435 K. What is the magnitude of the difference between the net power absorbed by the cube and the sphere? The surface area of a sphere is 4πr². TO TO

Imagine a physics lecture hall with 83 students who are settling in for a 1-hour lecture. At the start of the lecture, the temperature of the air in the room is a comfortable 70oF (21.1°C). Unfortunately, the room’s air conditioner breaks right as the lecture begins. Each student has an average power output of about 60.0 W at room temperature. Imagine the energy released by each student goes into heating just the air in the room, which has a volume of 9.50 × 102 m3 and a density of 1.20 kg/m3. Assume the volume of the air remains constant and the specific heat capacity of the air is 718 J/(kg · °C). Calculate the room’s temperature at the end of the lecture in oF (the answer may sound high (!), but in reality, a significant portion of the heat produced would be absorbed by the walls, ceiling, floors, chairs, desks, and so on, which we are neglecting).

A 150-g aluminum cup contains 750 g of water in thermal equilibrium with the cup at 90°C. The combination of cup and water is cooled uniformly so that the temperature decreases by 1.3°C per minute. At what rate is energy being removed? Express your answer in watts. ?W

Lead pellets, each of mass 1.00 g, are heated to 200°C. How many pellets must be added to 500 g of water that is initially at 20.0°C to make the equilibrium temperature 25.0°C? Neglect any energy transfer to or from the container.