KFUPM-Physics102-032

Dr.Aljalal

Sec07

Sec08

Sec09

Recitation ch 19

Answers at the end

Question 1

Calculate the amount of energy, in Joules, required to

completely melt 130 g of lead initially at temperature of

15.0 degrees Celsius. Melting point of lead = 328 degrees

Celsius, latent heat of fusion of lead = 2.32*10**4 J/kg

and the specific heat of lead = 128 J/kg/K.

a 1.31*10**4.

b 8.25*10**7.

c 3.02*10**3.

d 5.21*10**3.

e 8.22*10**3.

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Question 2

Two moles of a monatomic ideal gas at a temperature of 300 K

and pressure of 0.20 atm is compressed isothermally (constant

temperature) to a pressure of 0.80 atm. Find the work done by

the gas.

a 0 J

b +6900 J

c -6900 J

d +18000 J

e -18000 J

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Question 3

On a cold winter day, metallic objects generally feel

cooler to the touch than wooden objects.

This is because:

a the equilibrium temperature of metal is lower than

that of wood.

b the mass density of wood is less than the mass

density of metals.

c a given mass of wood contains more heat than the same

mass of metal.

d metals conduct heat better than wood.

e heat tends to flow from metal to wood.

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Question 4

A steel washer (ring) has an inner diameter of 4.000 cm and

an outer diameter of 4.500 cm at 20 deg C. To what temperature

must the washer be heated to just fit over a rod that is

4.010 cm in diameter?

(Coefficient of linear expansinon of steel, alpha,

= 11*10**-6 per C deg)

a 315 deg C

b 247 deg C

c -40 deg C

d 100 deg C

e 509 deg C

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Question 5

Gas within a closed chamber undergoes the cycle shown in

Fig. 2. Calculate the net heat added to the system in a

complete cycle.

a 14 J.

b 31 J.

c 10 J.

d 73 J.

e 60 J.

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Question 6

A metal rod has a length of 10.000 cm at 20 degrees-C,

and a length of 10.025 cm at the boiling point of water.

What is the temperature if the length of the rod is

10.015 cm ?

a 68 degrees-C

b 70 degrees-C

c 74 degrees-C

d 50 degrees-C

e 56 degress-C

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Question 7

A room has a window made of two layers of glass separated

by an air layer as in figure 4. Each of the 3 layers has

a thickness of 0.50 mm and an area of 1.0 square meter.

The temperature outside the room is - 20 degrees-C, while

the temperature inside the room is + 20 degrees-C.

What is the rate of heat transfer by conduction through

the window ? Assume steady state.

a 1.0 kW

b 2.0 kW

c 0.90 kW

d 1.2 kW

e 1.4 kW

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Question 8

A cylindrical copper rod of length 1.5 m and cross section

6.5 cm**2 is insulated to prevent heat loss through its surface.

The ends are maintained at a temperature difference of

100 C deg by having one end in a water-ice mixture and the

other in boiling water and steam. How much ice is melted per

hour at the cold end?

(thermal conductivity of copper, kappa, = 401 W/(m.K);

heat of fusion of ice, Lf, = 333*10*3 J/kg )

a 980 g

b 469 g

c 330 g

d 188 g

e 281 g

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Question 9

In an insulated container, 250 grams of ice at

0 degrees-C are added to 500 grams of water at

18 degrees-C.

How much ice remains when the system reaches equilibrium ?

[The latent heat of fusion of water = 333 kJ/kg and

the specific heat of water = 4190 J/kg.K].

a 79.0 g

b 113 g

c 250 g

d 137 g

e 300 g

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Question 10

Liquid nitrogen boils at temperature of -196 degrees Celsius

when the pressure is one atmosphere. A silver coin of

mass 1.5*10**(-2) Kg and temperature 25 degrees Celsius

is dropped into the liquid. What mass of nitrogen boils

off as the coin cools to – 196 degrees Celsius.

[Take the specific heat of silver = 235 J/Kg/K and latent heat

of vaporization for liquid nitrogen is 2.0*10**5 J/Kg.

a 3.90 g.

b 89.0 g.

c 20.1 g.

d 8.10 g.

e 112 g.

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Question 11

A system undergoes an adiabatic process in which its

internal energy increases by 20 J. Which of the following

correctly describes changes in the system ?

a Heat: 20 J removed, Work: none

b Heat: none, Work: 20 J on the system

c Heat: 20 J added, Work: none

d Heat: none, Work: 20 J by the system

e Heat: 40 J added, Work: 20 J by the system

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Question 12

A 200-g copper piece was initially at a temperature of

325 degrees-C. It is then dropped into 2000 g of water

at a temperature of 5 degrees-C. Assuming that the

copper-water system is an isolated system, and the

water does not vaporize, find the heat gained by water.

The specific heat of copper is 0.0923 cal/g.K

The specific heat of water is 1.00 cal/g.K.

a 5850 calories

b 16000 calories

c 4600 calories

d 12200 calories

e 9500 calories

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Question 13

How much heat is required to melt ice of mass 500 g at -10

deg C to water at 0 deg C?

(specific heat of ice, c, = 2220 J/(kg.K);

heat of fusion of ice, Lf, = 333*10*3 J/kg )

a 8.45*10**5 J

b 2.05*10**5 J

c 9.05*10**5 J

d 1.78*10**5 J

e 3.01*10**5 J

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Question 14

A rod is made of two different metals, one piece has

length L and thermal conductivity K and the other piece

has a length 2 L and thermal conductivity 3 K. The rod

is situated between two heat reservoirs as shown in

Fig. 1. What is the steady state temperature at the

interface of the two pieces ?

a 35 Kelvin.

b 68 Kelvin.

c 60 Kelvin.

d 0 Kelvin.

e 333 Kelvin.

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Question 15

An ideal gas is taken through the cycle ABCA, shown in

figure 4. The work done along the paths AB, BC and CA,

are respectively:

a 2*Po*Vo, Po*Vo, -1.5*Po*Vo

b 2*Po*Vo, zero , +1.5*Po*Vo

c 2*Po*Vo, zero , -Po*Vo

d 2*Po*Vo, zero , -1.5*Po*Vo

e 2*Po*Vo, zero , -2*Po*Vo

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Question 16

Body A is at a higher temperature than Body B. When they are

placed in contact, heat will flow from A to B

a until both have the same temperature

b only if the volume of A is larger than that of B

c only if A has the greater internal energy content

d only if the specific heat of A is larger that that of B

e only if the thermal conductivity of A is greater than that of B

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Question 17

A cylindrical glass beaker of radius 1.5 cm contains 20 mL

of water at 5.0 degrees-C. What is the change in the water

level when the temperature rises to 90 degrees-C. Ignore

the change in the volume of the glass beaker.

[The coefficient of volume expansion of water is

2.1*10**-4 (degrees-C)**-1 and 1 mL = 1 cm**3].

a 16 mm

b 0.51 mm

c 0.35 mm

d 0.11 mm

e 360 mm

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Question 18

When the temperature of a sphere is raised by

75 degrees Celsius the sphere’s volume increases

by 6.9*10**(-5) m**3.If the original volume

is 1.8*10**(-2) m**3, find the coefficient of

linear expansion of the sphere.

a 5.1*10**(-5) (Celsius degrees)**(-1).

b 3.4*10**(-5) (Celsius degrees)**(-1).

c 9.0*10**(-5) (Celsius degrees)**(-1).

d 1.7*10**(-5) (Celsius degrees)**(-1).

e 2.8*10**(-5) (Celsius degrees)**(-1).

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Question 19

A gas is compressed at a constant pressure of 0.800 atm

from a volume of 9.00 L to a volume of 2.00 L.

In the process, 400 J of heat flows out of the gas.

What is the change in the internal energy of the gas ?

a - 166 J

b - 966 J

c 566 J

d 166 J

e - 566 J

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Question 20

An aluminum rod and an iron rod, each of length 20.0 cm

and radius 1.00 cm, are placed end to end, as in

figure 3. The sides of the rods are insulated.

The outer end of iron is at 80.0 degrees-C and that

of aluminum is at 20.0 degrees-C. In steady state,

what is the temperature at the junction of the two rods ?

[The thermal conductivity of aluminum = 235 W/m.K and

the thermal conductivity of iron = 14.0 W/m.K].

a 76.6 degrees-C

b 15.7 degrees-C

c 50.0 degrees-C

d 85.6 degrees-C

e 23.4 degrees-C

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Answers

1 e

2 c

3 d

4 b

5 e

6 a

7 b

8 d

9 d

10 a

11 b

12 a

13 d

14 e

15 d

16 a

17 b

18 d

19 d

20 e