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Physics 151 Sample Questions I Spring 1998

Temperature scales such as Celsius and Fahrenheit, and non-metric units o heat such as caloriesand !T"s are #ased on$%& the metric system'$!& the properties o an ideal gas'$C& the properties o (ater'$)& the *inetic theory o gases'$+& the (hims and ertile imagination o 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$%& eat and Temperature are eui.alent concepts'

$!& eat is a measure o /hotness/ or /coldness/, (hile Temperature is a measure oenergy transer'$C& Temperature is a measure o /hotness/ or /coldness/, (hile eat is a measure o energy

transer'$)& Temperature is simply the numerical .alue (e assign to heat'

0oom temperature2 corresponds to a temperature o 34C, (hich is$%& 68 F'$!& 397 '$)& all o the a#o.e'$+& none o the a#o.e'

The .olume o a sample o gas is proportional to its$%& Fahrenheit temperature'$!& Celsius temperature'$C& a#solute temperature'$)& pressure'

The *inetic-molecular theory o gases predicts that at a gi.en temperature$%& all o the molecules ha.e the same a.erage speed'$!& all the molecules o a gas ha.e the same a.erage energy'$C& light molecules ha.e lo(er a.erage energies than hea.y molecules'$)& light molecules ha.e higher a.erage energies than hea.y molecules'

The *inetic theory o an ideal gas predicts that at higher temperatures$%& the molecules in the gas still ha.e the same a.erage *inetic energy'$!& the a.erage *inetic energy o the molecules in a gas (ill increase'$C& the a.erage *inetic energy o the molecules in a gas (ill decrease'$)& *inetic theory says nothing a#out *inetic energy'

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The *inetic theory o an ideal gas can #e used to deri.e$%& Charless :a('$!& !oyles :a('$C& the ideal gas la('$)& all o the a#o.e'

The .olume o a gas is held constant (hile its temperature is raised' The pressure the gas e;ertson the (alls o its containers increases #ecause

$%& the masses o the molecules increases'$!& each molecule loses more energy (hen it stri*es the (all'$C& the molecules are in contact (ith the (all or a longer time'$)& the molecules ha.e higher a.erage speeds$+& the molecules stri*e the (all more oten and harder'

The volume of a gas is increased while its temperature is held constant. The pressurethe 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$%& eat and Temperature are eui.alent concepts'$!& eat is a measure o /hotness/ or /coldness/, (hile Temperature is a measure o

energy transer'$C& Temperature is a measure o /hotness/ or /coldness/, (hile eat is a measure o

energy transer'$)& Temperature is simply the numerical .alue (e assign to heat'

The natural direction o the heat lo( #et(een t(o reser.oirs depends upon$%& their temperatures'$!& their internal energy contents'$C& their pressures'$)& (hether they are in a solid, liuid or gaseous state'

%s a liuid solidiies$%& it a#sor#s heat'$!& it releases heat'

$C& its temperature increases'$)& its temperature decreases'$+& #oth $!& and $)&

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The rate at (hich heat is conducted through a sla# o material does notdepend upon$%& the elapsed time'$!& the temperature dierence #et(een the aces o the sla#'$C& the thic*ness o the sla#'$)& the area o the sla#'$+& the thermal conducti.ity o the material'

?etals are good conductors o heat #ecause$%& they contain ree electrons'$!& their atoms are relati.ely ar apart'$C& their atoms collide inreuently'$)& they ha.e relecting suraces'

The ideal thermal radiator $electromagnetic radiation& has a surace (hich is$%& hori=ontal'$!& lat #lac*'

$C& e;tremely shiney'$)& 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 irst la( o Thermodynamics$%& is simply a statement o conser.ation o energy'

$!& is only a gross appro;imation or real heat engines'$C& indicates ho( much energy can #e created rom nothing in a heat

engine'$)& says that a heat engine cannot #e any less than 144@ eicient'

% heat engine operates #y ta*ing heat in at a particular temperature and$%& con.erting it all to (or*'$!& con.erting some o it to (or* and e;hausting the rest at a higher temperature'$C& con.erting some o it to (or* and e;hausting the rest at the same temperature'$)& con.erting some o it to (or* and e;hausting the rest at a lo(er temperature'

% Carnot engine that operates #et(een the a#solute temperatures T1and T3$%& is the most eicient heat engine possi#le operating #et(een the t(o gi.en

temperatures'$!& %l(ays has an eiciency o 144@$C& has an eiciency typical o real heat engines'$)& al(ays has an eiciency o 4@'

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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 anywork required.

(D) all of the above.(E) none of the above.

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% las* (ith a .olume o 3'4: $3'4;14 -7m7& contains elium $acting as an ideal gas& at 744 and 1;14 5Pa' $1 atm o pressure&a& I the .olume is reduced to one eighth o its original .alue, (hile maintaining the original temperature,(hat is the ne( pressureB#&

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TheDr. Gallis Thermal IQ test%n aluminum suare is to #e inserted into around hole in a steel suare' %t a commontemperature o 34 DC the 84'1 mm suare is '1 mm $'45 mm each side& too large to it in the84 mm round hole' To (hat commontemperature must the plate and peg #e #roughtso that the suare peg (ill it the round holeB

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% steel piston 84 mm in diameter mo.es insidean aluminum cylinder (ith a clearance o '1mm at 34 C' %t (hat common temperature(ill the t(o ha.e e;actly the same diameter,so that the piston can no longer mo.eB

80mm

.1mm

Not to Scale!

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% rod 3'4 m long e;pands #y 1'4 mm (hen heated rom 8 C to E4C'

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How much heat is required to turn 5kg of iceat -10 C to waterat 20 C?

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o( much energy $in >oules& is reuired to$%& raise the temperature o 1 *g o ice rom -54 C to 4 CB$!& completely melt 1 *g o ice at 4 CB$C& raise the temperature o 1 *g o (ater rom 4 C to 144 CB$)& completely con.ert to steam 1 *g o (ater at 144 CB$+& raise the temperature o 1 *g o steam rom 144 C to 154 CB$F& con.ert 1*g o ice at -54C to steam at 154 CB

---------------------------------------------------------------------------------------------------------------------I '34 *g o coee $treated as (ater& at 94C is poured into a '74 *g glass cup at 34C' %ssumingno heat is transerred to or rom the outside, (hat is the inal temperature o the coee $and cup&'

---------------------------------------------------------------------------------------------------------------------o( much heat $in oules& must #e remo.ed to con.ert 5'4 *g o steamat 154'4 DC to iceat

54' DCB

---------------------------------------------------------------------------------------------------------------------%n insulated copper rod 14mm on a side and 1m long has one end in a steam #ath at 144 C and the otherin contact (ith a #loc* o ice at 4 C'

$%& %t (hat rate is heat conducted through the copper rodB $

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+ach cycle, Carnot engine a#sor#s 344 * o heat at 344C and e;hausts 154 *'$a& o( much (or* is done each cycleB$#&

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