Q. Water flows straight down from an open faucet. The cross-sectional area of the faucet is 2.00 x10-4 m2, and the speed of the water is 0.87m/s as it leaves the faucet. Ignoring air resistance, find the cross-sectional area of the water stream at a point 0.11 m below the faucet.
Q. The concrete wall of a building is 0.140m thick. The temperature inside the building is 18.2 °C, even as the temperature outside is 0.0°C. Heat is conducted through the wall. When the building is unheated, the inside temperature falls to 0.0°C and heat conduction ceases. However, the wall does emit radiant energy while its temperature is 0.0°C. The radiant energy emitted per second per square meter is the same as the heat lost per second per square meter due to conduction. What is the emissivity of the wall?