Physics Test 4 answers

In an experiment to determine Absolute Zero, a straight line graph was obtained. The equation for the line was P = .05T + 14. Based on this data the experimental value of Absolute Zero in oC was

-280

A temperature of -40o C is equal to a temperature of how many degrees Fahrenheit?

-40°F

The coefficient of linear expansion for steel is 1.20 x 10-5/oC. Suppose 2.00 x 102 m long steel rod is heated from 0.0 oC to 100.0oC. By how many meters will the steel expand?

0.24

A heat engine operates between a hot temperature of 227oC and a cold temperature of -73oC The maximum efficiency of this engine?

0.60

1000 calories of heat is transferred from an object at 127oC to object at 27oC. By how much has the Entropy of the universe increased?

0.8 cal/°K

The only way that a heat engine can have an efficiency of 1, is if the engine's cold temperature is

0oK

A steel wire, 300 m long at 10°C, has a coefficient of linear expansion of 11 ´ 10-6/C°. What is its change in length as the temperature changes from 10°C to 45°C.

11.6 cm

A metal bar is used to conduct heat. When the temperature at one end is 100°C and at the other is 20°C, heat is transferred at a rate of 16 J/s. If the temperature of the hotter end is reduced to 80°C, what will be the rate of heat transfer?

12 J/s

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

A 0.003 0-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 = 4 186 J)

2.6 ´ 10-4 kg

The efficiency of a Carnot engine operating between 100oC and 0oC is most nearly:

27%

Normal room temperature 20oC. What is this temperature in degrees Kelvin?

293

A system is acted on by its surroundings in such a way that it receives 50 J of heat while simultaneously doing 20 J of work. What is its net change in internal energy?

30 J

A heat engine receives 6 000 J of heat from its combustion process and loses 4 000 J through the exhaust and friction. What is its efficiency?

33%

1 Calorie of food is equal to which of the following?

4 186 J

A substance is heated from 25oC to 65oC. The change is recorded as 40Co. What would the same change be when recorded in Kelvin degrees

40Ko

A gasoline engine with an efficiency of 30.0% operates between a high temperature T1 and a low temperature T2 = 320 K. If this engine operates with Carnot efficiency, what is the high side temperature T1?

457 K

A turbine takes in 1000-K steam and exhausts the steam at a temperature of 500 K. What is the maximum theoretical efficiency of this system?

50%

A long steel beam has a length of fifty meters on a cold day when the temperature is 0°C. What is the length of the beam on a hot day when T = 40°C? (asteel= 1.1 ´ 10-5/C°)

50.022 m

A person consumes 2 500 kcal/day while expending 3 500 kcal/day. In a month's time, about how much weight would this person lose if the loss were essentially all from body fat? (Body fat has an energy content of about 4 100 kcal per pound.)

7 pounds

20.0 g of ice at a temperature of 0oC is dropped into 160 g of water initially at a temperature 24.0oC. The final equilibrium temperature after all the ice has melted is 12.0oC. Based on this data the heat of fusion of ice was

84 cal

If an object scaled up by a factor of 3 (s = 3), the rate of heat loss from the surface of the object increases by a factor of

9

A 10-kg piece of aluminum (which has a specific heat of 900 J/kg×°C) is warmed so that its temperature increases by 10.0 C°. How much heat was transferred into it?

9.0 × 104 J

When considering human metabolism in terms of the 1st Law of Thermodynamics, which of the following represents the metabolic rate?

DU / Dt

What happens to a given mass of water as it is heated from 2oC to 4oC?

It contracts

Which of the following statements is true?

Objects do not contain heat.

Which of the following involves the greatest heat transfer?

One gram of steam at 100oC changing to water at 100oC.

Perpetual motion machines are not allowed by the

Second Law of Thermodynamics

Which of the following produces greenhouse gases?

all of these produce greenhouse gases

What is the mathematical relationship between the coefficient of volume expansion, b, for given material and its corresponding coefficient of linear expansion, a?

b = 3a

The maximum theoretical thermodynamic efficiency of a heat engine operating between hot and cold reservoirs is a function of which of the following?

both hot and cold reservoir temperatures

A bimetallic strip made of steel and brass bends toward the steel because

brass has a greater coefficient of linear expansion than steel.

According to the second law of thermodynamics, which of the following applies to the heat received from a high temperature reservoir by a heat engine operating in a complete cycle?

cannot be completely converted to work

Heat is transferred from the equator to the polar regions primarily by

convection

Which one of the following processes of heat transfer requires the presence of a fluid?

convection

Entropy is a measure of the ___________ of a system.

disorder

Which of the following choices best corresponds to what is required by the second law of thermodynamics for any process taking place in an isolated system?

entropy increases

In 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:

get warmer

Evaporation cools the liquid that is left behind because the molecules that leave the liquid during evaporation:

have greater than average speed

A steel plate has a hole drilled through it. The plate is put into a furnace and heated. What happens to the size of the inside diameter of a hole as its temperature increases?

increases

According to the first law of thermodynamics, the sum of the heat gained by a system and the work done on that same system is equivalent to which of the following?

internal energy change

50 grams of a solid at 50°C is place in 100 grams of a fluid at 20°C. Thermal equilibrium is reached at 30°C. The specific heat of the solid:

is equal to that of the fluid.

The absolute temperature of an ideal gas is directly proportional to which of the following properties, when taken as an average, of the molecules of that gas?

kinetic energy

During an isobaric process which one of the following does not change?

pressure

How does the heat energy from the sun reach us through the vacuum of space?

radiation

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?

radiation

Which type of heating causes sunburn?

radiation

What property of objects that is most used to measure temperature?

solids, liquids, and gases usually expand when heated.

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?

specific heat

Heat flow occurs between two bodies in thermal contact when they differ in what property?

temperature