Physics 151
Sample Questions I
Spring 1998
Temperature scales such as Celsius and Fahrenheit, and non-metric units of heat such as calories
and BTUs are based on
(A) the metric system.
(B) the properties of an ideal gas.
(C) the properties of water.
(D) the kinetic theory of gases.
(E) the whims and fertile imagination of scientists.
Absolute zero may be regarded as that temperature at which
(A) water freezes.
(B) all gases condense.
(C) all substances are solid.
(D) molecular motion in a gas is at the minimum possible.
Choose the most correct statement
(A) Heat and Temperature are equivalent concepts.
(B) Heat is a measure of "hotness" or "coldness", while Temperature is a measure of
energy transfer.
(C) Temperature is a measure of "hotness" or "coldness", while Heat is a measure of energy
transfer.
(D) Temperature is simply the numerical value we assign to heat.
“Room temperature” corresponds to a temperature of 20°C, which is
(A) 68° F.
(B) 293 K.
(D) all of the above.
(E) none of the above.
The volume of a sample of gas is proportional to its
(A) Fahrenheit temperature.
(B) Celsius temperature.
(C) absolute temperature.
(D) pressure.
The kinetic-molecular theory of gases predicts that at a given temperature
(A) all of the molecules have the same average speed.
(B) all the molecules of a gas have the same average energy.
(C) light molecules have lower average energies than heavy molecules.
(D) light molecules have higher average energies than heavy molecules.
The kinetic theory of an ideal gas predicts that at higher temperatures
(A) the molecules in the gas still have the same average kinetic energy.
(B) the average kinetic energy of the molecules in a gas will increase.
(C) the average kinetic energy of the molecules in a gas will decrease.
(D) kinetic theory says nothing about kinetic energy.
1
Physics 151
Sample Questions I
Spring 1998
The kinetic theory of an ideal gas can be used to derive
(A) Charles's Law.
(B) Boyle's Law.
(C) the ideal gas law.
(D) all of the above.
The volume of a gas is held constant while its temperature is raised. The pressure the gas exerts
on the walls of its containers increases because
(A) the masses of the molecules increases.
(B) each molecule loses more energy when it strikes the wall.
(C) the molecules are in contact with the wall for a longer time.
(D) the molecules have higher average speeds
(E) the molecules strike the wall more often and harder.
The volume of a gas is increased while its temperature is held constant. The pressure
the gas exerts on the walls of its containers increases because
(A) the masses of the molecules increases.
(B) each molecule loses more energy when it strikes the wall.
(C) the molecules are in contact with the wall for a longer time.
(D) the molecules have higher average speeds
(E) the molecules strike the wall more often and harder.
Choose the most correct statement
(A) Heat and Temperature are equivalent concepts.
(B) Heat is a measure of "hotness" or "coldness", while Temperature is a measure of
energy transfer.
(C) Temperature is a measure of "hotness" or "coldness", while Heat is a measure of
energy transfer.
(D) Temperature is simply the numerical value we assign to heat.
The natural direction of the heat flow between two reservoirs depends upon
(A) their temperatures.
(B) their internal energy contents.
(C) their pressures.
(D) whether they are in a solid, liquid or gaseous state.
As a liquid solidifies
(A) it absorbs heat.
(B) it releases heat.
(C) its temperature increases.
(D) its temperature decreases.
(E) both (B) and (D)
2
Physics 151
Sample Questions I
Spring 1998
When gas condenses into a liquid,
(A) it absorbs heat.
(B) it releases heat.
(C) its temperature rises.
(D) its temperature drops.
(E) none of the above
When a solid melts
(A) it absorbs heat.
(B) it releases heat.
(C) its temperature increases.
(D) its temperature decreases.
(E) both (B) and (C)
The substance which will require the greatest amount of heat per kilogram for a given increase in
temperature is the one with
(A) the greatest specific heat
(B) the smallest specific heat.
(C) the greatest latent heat of fusion.
(D) the smallest latent heat of vaporization.
In natural convection a heated portion of the fluid moves because
(A) its molecular motions become aligned.
(B) of molecular collisions within it.
(C) its density is less than that of the surrounding fluid, resulting in a buoyant force.
(D) of the currents in the surrounding fluid.
Heat transfer by conduction occurs
(A) only in solids.
(B) only in liquids.
(C) only in solids or liquids.
(D) only in liquids or gases.
(E) in solids, liquids or gases.
An object will emit thermal electromagnetic radiation
(A) when its temperature is above its freezing point.
(B) when its temperature is above its boiling point.
(C) when its temperature is above absolute zero.
(D) never.
The rate at which an object radiates electromagnetic energy does not depend upon its
(A) surface area.
(B) temperature.
(C) mass.
3
Physics 151
Sample Questions I
Spring 1998
(D) ability to absorb radiation.
4
Physics 151
Sample Questions I
Spring 1998
The rate at which heat is conducted through a slab of material does not depend upon
(A) the elapsed time.
(B) the temperature difference between the faces of the slab.
(C) the thickness of the slab.
(D) the area of the slab.
(E) the thermal conductivity of the material.
Metals are good conductors of heat because
(A) they contain free electrons.
(B) their atoms are relatively far apart.
(C) their atoms collide infrequently.
(D) they have reflecting surfaces.
The ideal thermal radiator (electromagnetic radiation) has a surface which is
(A) horizontal.
(B) flat black.
(C) extremely shiney.
(D) clear.
The first law of thermodynamics is a statement about
(A) conservation of energy.
(B) conservation of momentum.
(C) conservation of temperature.
(D) the efficiency of the Carnot Cycle.
The first law of Thermodynamics
(A) is simply a statement of conservation of energy.
(B) is only a gross approximation for real heat engines.
(C) indicates how much energy can be created from nothing in a heat
engine.
(D) says that a heat engine cannot be any less than 100% efficient.
A heat engine operates by taking heat in at a particular temperature and
(A) converting it all to work.
(B) converting some of it to work and exhausting the rest at a higher temperature.
(C) converting some of it to work and exhausting the rest at the same temperature.
(D) converting some of it to work and exhausting the rest at a lower temperature.
A Carnot engine that operates between the absolute temperatures T1 and T2
(A) is the most efficient heat engine possible operating between the two given
temperatures.
(B) Always has an efficiency of 100%
(C) has an efficiency typical of real heat engines.
(D) always has an efficiency of 0%.
5
Physics 151
Sample Questions I
Spring 1998
A refrigerator is
(A) a heat engine run in reverse.
(B) violates the second law of thermodynamics.
(C) Can transfer heat from a cold temperature to a hot temperature without any
work required.
(D) all of the above.
(E) none of the above.
6
Physics 151
Sample Questions I
Spring 1998
A flask with a volume of 2.0L (2.0x10-3 m3) contains Helium (acting as an ideal gas) at 300 K and 1x105
Pa. (1 atm of pressure)
a) If the volume is reduced to one eighth of its original value, while maintaining the original
temperature, what is the new pressure?
b) What is the new volume if the gas is now heated to 900 K while maintaining the pressure found in
part (b)?
c) What is the pressure if the gas is finally allowed to cool back to 600K and the volume is taken back
to the original value from the beginning of the problem?
--------------------------------------------------------------------------------------------------------------------A sample of gas occupies 4 m3 at 27 °C and a pressure of 2 x 105 Pa.
(a) What is its pressure at the same volume when the temperature has been raised to 600
°C?
(b) What is the volume at the original temperature (27 °C) when the pressure has been
decreased to 4.0x105 Pa?
(c) At what temperature will the volume is 8 m3 and the pressure is 1.0x105 Pa?
--------------------------------------------------------------------------------------------------------------------N ot to S cale!
The Dr. Gallis Thermal IQ test!
An aluminum square is to be inserted into a
round hole in a steel square. At a common
temperature of 20 ˚C the 80.1 mm square is
.1 mm (.05 mm each side) too large to fit in
the 80 mm round hole. To what common
temperature must the plate and peg be brought
so that the square peg will fit the round hole?
80mm
.05m
m
---------------------------------------------------------------------------------------------------------------------
7
Physics 151
Sample Questions I
A steel piston 80 mm in diameter moves inside
an aluminum cylinder with a clearance of .1
mm at 20 ºC. At what common temperature
will the two have exactly the same diameter,
so that the piston can no longer move?
Spring 1998
Not to S cale!
80mm
.1mm
--------------------------------------------------------------------------------------------------------------------A rod 2.0 m long expands by 1.0 mm when heated from 8C to 70C. What is the coefficient of linear
expansion of the material from which the rod is made?
--------------------------------------------------------------------------------------------------------------------A 250 cm3 container made of quartz is completely filled with ethanol, and both are at 15
°C. When the container and contents area heated, 5 cm3 overflows. What is the new
temperature of the container and contents?
--------------------------------------------------------------------------------------------------------------------Hydrogen (H2) has a molecular weight of 2 grams/mole. At 27 °C,
(A) What is the average kinetic energy of a single hydrogen molecule?
(B) What is the rms speed of a hydrogen molecule?
(C)-(D) Repeat (A) and (B) for Oxygen (O2) which has a molecular weight
of 32 grams/mole.
--------------------------------------------------------------------------------------------------------------------How much heat (in Joules) is required to turn 20.0 kg of water at 50.0 ˚C to steam at 150. ˚C?
--------------------------------------------------------------------------------------------------------------------How much heat is required to turn 5kg of ice at -10 ˚C to water at 20 ˚C?
---------------------------------------------------------------------------------------------------------------------
8
Physics 151
Sample Questions I
Spring 1998
How much energy (in joules) is required to
(A) raise the temperature of 1 kg of ice from -50 °C to 0 °C?
(B) completely melt 1 kg of ice at 0 °C?
(C) raise the temperature of 1 kg of water from 0 °C to 100 °C?
(D) completely convert to steam 1 kg of water at 100 °C?
(E) raise the temperature of 1 kg of steam from 100 °C to 150 °C?
(F) convert 1kg of ice at -50°C to steam at 150 °C?
--------------------------------------------------------------------------------------------------------------------If .20 kg of coffee (treated as water) at 90°C is poured into a .30 kg glass cup at 20°C. Assuming
no heat is transferred to or from the outside, what is the final temperature of the coffee (and cup).
--------------------------------------------------------------------------------------------------------------------How much heat (in Joules) must be removed to convert 5.0 kg of steam at 150.0 ˚C to ice at 50.
˚C?
--------------------------------------------------------------------------------------------------------------------An insulated copper rod 10mm on a side and 1m long has one end in a steam bath at 100 °C and the
other in contact with a block of ice at 0 °C.
(A) At what rate is heat conducted through the copper rod? (Watts)
(B) How much ice is melted in one hour? (kg)
--------------------------------------------------------------------------------------------------------------------An igloo of compacted snow has a surface area of 24 m2 and a wall thickness of .40 m.
The thermal conductivity of the snow is 8.37 x 10 kJ/(m.s.˚C). The inside temperature
is 20 ˚C and the outside temperature is -10˚C.
(A) What is the rate of heat loss?
(B) How many Joules of heat are lost over one hour?
(C) How many kg of blubber must be burned if each kg of blubber releases 40,000,000 J
(40 MJ) when burned?
--------------------------------------------------------------------------------------------------------------------A house window contains a pane of glass 0.800 m wide , 1.00 m tall and 6.00 mm thick. The
glass has a thermal conductivity of 0.800 W/m˚C If the inner and outer faces of the glass are at
20 ˚C and 0.0 ˚C, respectively, what is the rate of heat loss through the window?
--------------------------------------------------------------------------------------------------------------------A Carnot engine takes in 1.0 MJ of heat each cycle and exhausts waste heat to a reservoir at 127
˚C. The efficiency of the engine is to be 50%.
(A) At what temperature (in ˚C) must the intake heat be supplied to achieve this efficiency?
(B) How much work is done each cycle?
(C) How much waste heat is exhausted each cycle?
---------------------------------------------------------------------------------------------------------------------
9
Physics 151
Sample Questions I
Spring 1998
Each cycle, Carnot engine absorbs 200 kJ of heat at 200°C and exhausts 150 kJ.
(a) How much work is done each cycle?
(b) What is the exhaust temperature?
(c) What is the efficiency of the engine?
--------------------------------------------------------------------------------------------------------------------One of the most efficient heat engines ever developed operates between about 2300 ˚C
and 1000 ˚C. Its actual efficiency is 40%.
a) What is the maximum possible efficiency of this heat engine?
b) What percentage of the maximum efficiency is the actual efficiency?
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