A student makes some tea. Its temperature is 45 oC when they finish making it. They want to drink some right away. How much ice at 0 oC should they put in a cup containing 0.5 liters of tea to cool it to 3 oC? Assume tea has the same properties as water.
1. A birdbath shoots water from a 0.5 mm diameter opening. The water rises 10 cm above the nozzle.
a. Calculate the speed of the water leaving the opening.
b. The water line going to the birdbath has an inner diameter of inch. Calculate the speed of the water in the water line.
c. How much water does the birdbath use in one hour?
2. A child wanders away from home on a fall day. The temperature overnight is 20 oC. Their skin temperature is 37 oC.
a. Calculate the net rate of heat flow away from their body. Assume their skin has a surface area of 0.9 m2 and an emissivity of 0.97. Ignore the insulating effects of their clothing.
b. At what rate must their metabolism provide energy to keep their body temperature from decreasing?