an inventor develops a stationary cycling device by which an individual, while pedaling, can convert...
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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 gm of water (enough for 1 cup of coffee) from 20°C to 95°C? (1 cal = 4.186 J)
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1. 94,000 Joules
2. 22,000 Joules
3. 5400 Joules
4. 13.9 Joules
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 gm 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)
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1. 9400 watts
2. 586 watts
3. 160 watts
4. 31 watts
A falling 500 kg object is attached by a rope through a pulley to a paddle wheel shaft which is placed in a well-insulated tank holding 25 kg of water. The object, in being allowed to fall, causes the paddle wheel to rotate to churn the water. If the object falls a vertical distance of 100 m at constant speed, what is the temperature change of the water? (1 Kcalorie = 4186 J and g = 9.8 m/s2 )
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1. 19600°C
2. 4700°C
3. 4.7°C
4. 0.8°C
Sea breezes that occur near the shore are attributed to a difference between land and water with respect to what property?
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1. mass density
2. coefficient of volume expansion
3. specific heat
4. emissivity
Which of the following processes of heat transfer may take place in a vacuum?
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1. conduction
2. radiation
3. convection
4. None of these choices are valid
Which one of the following processes of heat transfer require the presence of a fluid?
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1. conduction
2. radiation
3. convection
4. None of these choices are valid
If cooking is done using an aluminum pan over an electric burner, which of the following will not promote the rate of heat flow from burner to food?
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1. increase pan bottom thickness
2. increase pan bottom area
3. increase burner temperature
4. decrease height of pan sides
The first experiment which systematically demonstrated the equivalence of mechanical energy and heat was performed by which of the following scientists?
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1. Joule
2. Boltzmann
3. Thompson, Count Rumford
4. Kelvin
On a sunny day at the beach, the reason the sand gets so hot and the water stays relatively cool is attributed to the difference in which property between water and sand?
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1. mass density
2. specific heat
3. temperature
4. thermal conductivity
The surfaces of a Dewar flask are silvered for the purpose of minimizing heat transfer by what process?
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1. conduction
2. radiation
3. convection
4. vaporization
The use of fiberglass insulation in the outer walls of a building is intended to minimize heat transfer through what process?
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1. conduction
2. radiation
3. convection
4. vaporization
A 200 gm mass of metal with a specific heat of 0.30 cal/gm-°C, initially at 90°C, is placed in a 500 gm calorimeter initially at 20° C with a specific heat of 0.10 cal/gm-°C. The calorimeter is filled with 100 gm of water initially at 20°C. Once the combination of metal, calorimeter and water reach equilibrium, what is the final temperature?
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1. 70°C
2. 60°C
3. 50°C
4. 40°C
Heat flow occurs between two bodies in thermal contact when they differ in what property?
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1. mass
2. specific heat
3. density
4. temperature
If one's hands are being warmed by holding them to one side of a flame, the predominant form of heat transfer is what process?
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1. conduction
2. radiation
3. convection
4. vaporization
The first experimental observation which tended to disprove the caloric model of heat was made by which of the following scientists?
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1. Joule
2. Boltzmann
3. Thompson, Count Rumford
4. Kelvin
A 20 gm object has what specific heat if its temperature increases by 5°C when 20 cal of heat are transferred to it?
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1. 0.20 cal/gm-°C
2. 0.40 cal/gm-°C
3. 0.60 cal/gm-°C
4. 0.85 cal/gm-°C
In a greenhouse, electromagnetic energy in the form of visible light enters the glass panes and is absorbed and then reradiated. What happens to this reradiated electromagnetic radiation from within the greenhouse?
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1. 100% returns to the atmosphere
2. blocked by glass
3. transformed into ultraviolet upon striking the glass
4. reflected as visible light upon striking the glass
Which of the following best describes a substance in which the temperature remains constant while at the same time it is experiencing an inward heat flow?
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1. gas
2. liquid
3. solid
4. substance undergoing a change of state
A copper rod has one of its ends placed in a Bunsen flame and the other end embedded in an ice cube. By what factor is the rate of heat flow changed when the rod length is tripled?
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1. 0.33
2. 1/9
3. 3.0
4. 9.0
A copper rod has one of its ends placed in a heat reservoir and the other end in a heat sink. By what factor is the rate of heat flow changed when the temperature difference between the reservoir and sink is tripled?
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1. 0.33
2. 1/9
3. 3.0
4. 9.0
The surface of the sun has a temperature of about 5800 K. If the radius of the sun is 7 x 108 m, determine the power output of the sun. (Take S = 1, and s = 5.67 x 10-8 W/m2 /K4 )
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1. 3.95 x 1026 W
2. 5.17 x 1027 W
3. 9.62 x 1028 W
4. 6.96 x 1030 W
The tungsten filament of a lightbulb has an operating temperature of about 2100 K. If the emitting area of the filament is 1 cm2 , and its emissivity is 0.68, what is the power output of the lightbulb? (s = 5.67 x 10-8 W/m2 x K4 )
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1. 100 W
2. 75 W
3. 60 W
4. 40 W
A 5 - gram lead bullet traveling in 20°C air at 300 m/s strikes a flat steel plate and stops. What is the final temperature of the lead bullet? (Assume all heat is retained by the bullet). The melting point of lead is 327°C. The specific heat of lead is 0.122 J/g/°C. The heat of fusion of lead is 24.7 J/g.
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1. 227°C
2. 260°C
3. 293°C
4. 327°C
A slice of bread contains about 100 kilo-calories. If the specific heat of a person is 1 kilocalorie/kg x°C, by how many °C would the temperature of a 70-kg person increase if all the energy in the bread were converted to heat?
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1. 2.25°C
2. 1.86°C
3. 1.43°C
4. 1.00°C
At high noon, the sun delivers 1000 watts to each square meter of a blacktop road. What is the equilibrium temperature of the hot asphalt? (s = 5.67 x 10-8 W/m2 / °K4 )
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1. 75°C
2. 84°C
3. 91°C
4. 99°C
A silver bar of length 30 cm and cross-sectional area 1 cm2 is used to transfer heat from a 100°C reservoir to a 0°C block of ice. How much ice is melted per second? (For silver, k = 427 W/m x °C. For ice, Lf = 334,000 J/kg.)
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1. 4.2 grams/s
2. 2.1 grams/s
3. 0.8 grams/s
4. 0.042 grams/s
Find the final equilibrium temperature when 10 grams of milk at 10°C is added to 160 grams of coffee at 90°C. (Assume the specific heats of coffee and milk are the same as water and neglect the heat capacity of the container).
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1. 85.3°C
2. 77.7°C
3. 71.4°C
4. 66.7°C
How much heat energy is required to vaporize a 1 - gram ice cube at 0°C? The heat of fusion of ice is 80 calories/gram. The heat of vaporization of water is 540 cal/gram.
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1. 620 calories
2. 720 calories
3. 820 calories
4. 1 kilocalorie
How much heat energy must be removed from 100 grams of oxygen at 22°C to liquify it at -183°C? (The specific heat of oxygen gas is 0.218 cal/g-°C and its heat of vaporization is 50.9 cal/gram.)
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1. 13,652 cal
2. 9,559 cal
3. 4,316 cal
4. 2,160 cal
100 grams of liquid nitrogen at 77° K is stirred into a beaker containing 500 grams of 15°C water. If the nitrogen leaves the solution as soon as it turns to gas, how much water freezes? The heat of vaporization of nitrogen is 48 cal/gram. The heat of fusion of water is 80 cal/gm.
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1. none
2. 29 grams
3. 68 grams
4. 109 grams
In winter, light colored clothes will keep you warmer than dark colored clothes if
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1. you are warmer than your surroundings.
2. you are at the same temperature as your surroundings.
3. you are cooler than your surroundings.
4. you are standing in sunlight.
I take 1 kg of ice and dump it into 1 kg of water and, when equilibrium is reached, I have 2 kg of ice. The water was originally at 0°C. The specific heat of water = 1 kcal/kg-°C, the specific heat of ice = 0.5 kcal/kg-°C, and the latent heat of fusion of water is 80 kcal/kg-°C. The original temperature of the ice was
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1. one or two degrees below 0°C
2. -80°C
3. -160°C
4. the whole experiment is impossible.
Consider two different rods and predict which will have the greatest thermal conductivity. The rod with
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1. electrons that are freer to move from atom to atom.
2. the greater specific heat.
3. the greater cross-sectional area.
4. the greater length.
Which type of heating causes sunburn?
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1. conduction
2. convection
3. radiation
4. all of these cause sunburn
Carbon dioxide and water molecules in the atmosphere will absorb
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1. infrared light.
2. visible light.
3. ultraviolet light.
4. radio waves.
In a cloud formation, water vapor turns into water droplets which get bigger and bigger until it rains. This will cause the temperature of the air in the clouds to
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1. get warmer.
2. get cooler.
3. will not affect the temperature of the air in the clouds.
4. there is no air in clouds.
Active solar heating involves the use of
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1. convection currents.
2. air locks.
3. pumps.
4. the greenhouse effect.
A 120-gram block of copper is taken from a kiln and carefully placed into a beaker containing 300 grams of water. The water temperature rises from 15°C to 35°C. Given cCu = 0.10
cal/gram-°C, and cwater = 1.00 cal/gram-°C, what was the
temperature of the kiln?
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1. 500°C
2. 360°C
3. 720°C
4. 535°C
125 grams of dry ice (solid CO2 ) is dropped into a beaker
containing 500 grams of 66°C water. The dry ice converts directly to gas, leaving the solution. When the dry ice is gone, the final temperature of the water is 29°C. What is the heat of vaporization of solid CO2 ?
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1. 37 cal/gram
2. 74 cal/gram
3. 111 cal/gram
4. 148 cal/gram
A piece of copper of mass 100 grams is being drilled through with a 1/2" electric drill. The drill operates at 40 W and takes 30 seconds to bore through the copper. The specific heat of copper is 387 J/kg-°C. Find the increase in its temperature.
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1. 40.6°C
2. 34.7°C
3. 31.0°C
4. 27.3°C
As I use sandpaper on some rusty metal, the sandpaper gets hot.
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1. Heat is flowing from the sandpaper into the metal.
2. Heat is flowing from the metal into the sandpaper.
3. Friction is creating the heat.
4. Heat is flowing from my hand into the sandpaper.
A 50 gm cube of ice, initially at 0°C is dropped into a 200 gm of water in an 80 gm aluminum container, both initially at 30°C. What is the final equilibrium temperature? (Specific heat for aluminum is 0.215 cal/gm-°C and Lf = 80 cal/gm.)
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1. 17.9°C
2. 9.4°C
3. 12.1°C
4. 20.6°C
If heat is flowing from a table to a block of ice moving across the table, which of the following must be true?
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1. The table is rough and there is friction between the table and ice.
2. The ice is cooler than the table.
3. The ice is changing phase.
4. All three are possible, but none is absolutely necessary.
A 500 gm ice cube, initially at 0°C, is placed in a styrofoam box whose wall thickness is 1.0 cm and the total surface area is 600 cm2 . If the air surrounding the box is at 20°C and after 4 hours the ice is completely melted, what is the conductivity of the styrofoam material? (Lf = 80 cal/gm)
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1. 9.6 x 10-5 cal/cm-sec-°C
2. 2.8 x 10-6 cal/cm-sec-°C
3. 1.15 x 10-2 cal/cm-sec-°C
4. 2.3 x 10-4 cal/cm-sec-°C
A solar heating system has a 25% conversion efficiency; the solar radiation incident on the panels is 1000 W/m2. What is the increase in temperature of 30 kg of water in a 1.0 hr period by a 4.0 m2 area collector?
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1. 14.3°C
2. 22.4°C
3. 28.6°C
4. 44.3°C
A 100 gm piece of copper, initially at 95°C, is dropped into 200 gm of water contained in a 280 gm aluminum calorimeter; the water and calorimeter are initially at 15°C. What is the final temperature of the system? (specific heats of copper and aluminum of 0.092 and 0.215 cal/gm-°C, respectively)
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1. 16.8°C
2. 18.3°C
3. 23.7°C
4. 25.0°C
A machine gear consists of 0.1 kg of iron and 0.16 kg of copper. How much total heat is generated in the part if its temperature increases by 35°C? (Specific heats of iron and copper are 0.11 and 0.092 kcal/kg/°C, respectively, and 1 kcal = 4186 J.)
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1. 910 J
2. 3770 J
3. 3980 J
4. 4420 J
What is the temperature increase of 4.0 kg of water when heated by a 800 W immersion heater for 10 min?
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1. 56°C
2. 51°C
3. 28°C
4. 14°C
Iced tea is made by adding ice to 1.8 kg of hot tea, initially at 80°C. How many kg of ice, initially at 0°C, are required to bring the mixture to 10°C? (Lf = 80 kcal/kg)
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1. 1.8 kg
2. 1.6 kg
3. 1.4 kg
4. 1.2 kg
The filament temperature of a light bulb is 2000 K when the bulb delivers 40 W of power. If its emissivity remains constant, what power is delivered if the filament temperature is raised to 2500 K?
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1. 105 W
2. 62 W
3. 98 W
4. 50 W
A waterfall is 145 m high. What is the increase in temperature of the water at the bottom of the falls if all of the initial potential energy goes into heating the water? (g = 9.8 m/s2 and 1 kcal = 4186 J)
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1. 0.16°C
2. 0.34°C
3. 0.69°C
4. 1.04°C
A 0.2 kg aluminum plate, initially at 20°C, slides down a 15 m long surface, inclined at a 30° angle to the horizontal. The force of kinetic friction exactly balances the component of gravity down the plane so that the plate, once started, glides down at constant velocity. If 90% of the mechanical energy of the system is absorbed by the aluminum, what is its temperature increase when at the bottom of the incline? (Specific heat for aluminum is 0.215 kcal/kg/°C and 1 kcal = 4186 J)
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1. 0.16°C
2. 0.08°C
3. 0.04°C
4. 0.03°C
How many kilo-watt hours of energy would be required to raise the temperature of a 30,000 gallon swimming pool by 5°C? (One gallon of water has a mass of approximately 3.8 kg and the specific heat of water is 4186 J/kgx°C.)
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1. 1047.7 kWH
2. 662.8 kWH
3. 330.0 kWH
4. 216.6 kWH
A solar heated house loses about 5.4 x 107 cal through its outer surfaces on a typical 24 hr 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/gm-°C.)
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1. 163 kg
2. 1,230 kg
3. 6,100 kg
4. 12,700 kg
A 2-m2 thermopane window is constructed, using two layers of glass 4 mm thick, separated by an air space of 5 mm. If the temperature difference is 20° from the inside of the house to the outside air, what is the rate of heat flow through this window? (Thermal conductivity for glass is 0.8 J/s x m x °C and for air 0.0234 J/s x m x °C.)
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1. 8000 W
2. 2000 W
3. 568 W
4. 179 W
A 0.003 kg lead bullet is traveling at a speed of 240 m/s when it embeds in a block of ice at 0°C. If all the heat generated goes into melting ice, what quantity of ice is melted? (Lf = 80 kcal/kg,
the specific heat of lead = 0.03 kcal/kg °C, and 1 kcal = 4186 J)
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1. 1.47 x 10-2 kg
2. 5.8 x 10-4 kg
3. 3.2 x 10-3 kg
4. 2.6 x 10-4 kg
A flat pan container holds 200 gm of water. If over a 10 min period, 1.5 gm of water evaporates from the surface, what is the approximate temperature change of the remaining water? (Lv = 540 cal/gm)
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1. +4°C
2. -4°C
3. +0.4°C
4. -0.4°C
A glass pane 0.4 cm thick has an area of 2 m2 . On a winter day the temperature difference between the inside and outside surfaces of the pane is 20°C. What is the rate of heat flow through this window? (Thermal conductivity for glass is 0.8 J/s x m x °C.)
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1. 32,000 J/s
2. 8,000 J/s
3. 4,000 J/s
4. 1,000 J/s
A 0.003 kg lead bullet is traveling at a speed of 240 m/s when it embeds in a wood post. If it assumed that half of the resultant heat energy generated remains with the bullet, what is the increase in temperature of the embedded bullet? (Specific heat of lead = 0.03 kcal/kg- °C, 1 kcal = 4186 J.)
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1. 115
2. 137
3. 230
4. 259