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The following physics responses are provided by a student and, as such, should be considered in that context. While every effort is made for accuracy, absolute correctness cannot be fully guaranteed.
| C | I | Question | Answer |
|---|---|---|---|
| 11 | A solar heated house loses about 5.4*10^7 cal through its outer surfaces on a typical 24-h winter day. What mass of storage rock is needed to provide this amount of heat if it is brought up to initial temperature of 62°C by the solar collectors and the house is maintained at 20°C? (Specific heat of rock is 0.21 cal/g×°C.) | 6100 kg | |
| 11 | A solar heating system has a 25.0% conversion efficiency; the solar radiation incident on the panels is 1000 W/m^2. What is the increase in temperature of 30.0 kg of water in a 1.00-h period by a 4.00m^2 -area collector? (cw = 4186 J/kg×°C) | 28.7°C | |
| 11 | A swimming pool heater has to be able to raise the temperature of the 40 000 gallons of water in the pool by 10.0 C°. How many kilowatt-hours of energy are required? (One gallon of water has a mass of approximately 3.8 kg and the specific heat of water is 4 186 J/kg×°C.) | 1770 kWh | |
| 11 | A waterfall is 145 m high. What is the increase in water temperature at the bottom of the falls if all the initial potential energy goes into heating the water? (g = 9.8 m/s^2 , cw = 4186 J/kg×°C) | 0.34°C | |
| 11 | A windowpane is half a centimeter thick and has an area of 1.0 m^2 . The temperature difference between the inside and outside surfaces of the pane is 15 C°. What is the rate of heat flow through this window? (Thermal conductivity for glass is 0.84 J/s*m*°C.) | 2500 J/s | |
| 11 | An 80.0-g piece of copper, initially at 295°C, is dropped into 250 g of water contained in a 300-g aluminum calorimeter; the water and calorimeter are initially at 10.0°C. What is the final temperature of the system? (Specific heats of copper and aluminum are 0.092 0 and 0.215 cal/g×°C, respectively. cw = 1.00 cal/g×°C) | 16.5°C | |
| 11 | An inventor develops a stationary cycling device by which an individual, while pedaling, can convert all of the energy expended into heat for warming water. How much mechanical energy is required to increase the temperature of 300 g of water (enough for 1 cup of coffee) from 20°C to 95°C? (1 cal = 4.186 J, the specific heat of water is 4 186 J/kg×°C) | 94000 J | |
| 11 | An inventor develops a stationary cycling device by which an individual, while pedaling, can convert all of the energy expended into heat for warming water. What minimum power must be generated if 300 g water (enough for 1 cup of coffee) is to be heated in 10 min from 20°C to 95°C? (1 cal = 4.186 J, the specific heat of water is 4 186 J/kg×°C) | 160 W | |
| 11 | An object at 27°C has its temperature increased to 37°C. The power then radiated by this object increases by how many percent? | 14 | |
| 11 | Arrange from smallest to largest: the BTU, the joule, and the calorie. | J, cal, BTU | |
| 11 | As I use sandpaper on some rusty metal, the sandpaper gets hot because: | frictional processes increase the internal energy of the sandpaper. | |
| 11 | At high noon, the sun delivers 1 000 W to each square meter of a blacktop road. What is the equilibrium temperature of the hot asphalt, assuming its emissivity e = 1? (s = 5.67*10^-8 W/m^2*K^4) | 91°C | |
| 11 | Calories of the food type are equal to which of the following? | 4186 J | |
| 11 | Carbon dioxide and water molecules in the atmosphere will absorb: | infrared light. | |
| 11 | Carly places one end of a steel bar in a Bunsen flame and the other end in an ice cube. By what factor is the rate of heat flow changed when the bar's cross-sectional area is doubled? | 2 |
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