APRIL TEST 2007 PHYSICS SMK TINGGI MELAKAAnswer all questions in obejctive answer sheet. 1. The ends of a cylindrical steel rod are maintained at two different temperatures. The rod conducts heat from one end to the other at a rate of 10 watt. At what rate would a steel rod twice as long and twice the diameter conduct heat between the same two temperatures? A) 5 watt B) 20 watt C) 40 watt D) 80 watt 2. The space between the inner walls of a thermos bottle is evacuated to minimize heat transfer by A) radiation. C) conduction and convection. B) conduction. D) conduction and radiation. 3. At what rate is heat lost through a 1.0 m 1.5 m rectangular glass windowpane that is 0.5 cm thick when the inside temperature is 20 C and the outside temperature is 5 C? The -1 -1 thermal conductivity for glass is 0.80 Wm K A) 18 W B) 36 W C) 720 W D) 3600 W 4. The two ends of an iron rod are maintained at different temperatures. The amount of heat that flows through the rod by conduction during a given time interval does not depend upon A) the length of the iron rod. B) the thermal conductivity of iron. C) the temperature difference between the ends of the rod. D) the mass of the iron rod. 5. A non-uniform metal rod is well lagged and its ends are maintained at different temperatures. At steady state, A) the temperature gradient along the rod is constant B) the rate of heat flow at any cross section of the rod is the same C) the temperature at every point along the rod is the same D) the rate of heat flow at any cross section of the rod is zero

Page 1

6. Two cylindrical steel rods A and B have radii of 0.02 m and 0.04 m, respectively. It is found that the two steel rods conduct the same amount of heat per unit time for the same temperature differences between their two ends. What is the ratio of the lengths of the rods, L /L ?A B

A) 0.25

B) 0.50

C) 1.00

D) 2.00

7. A slab of insulation is made of three layers, as Drawing I indicates. Each of the layers A, B, and C has the same thickness, but a different thermal conductivity. Heat flows through the slab, and the temperatures are as shown. What are the temperatures T and T In1 2

Drawing II where the layers are arranged in a different order?

A) T = 230 C and T = 170 C1 1 2 2

C) T = 220 C and T = 160 C1 1 2 2

B) T = 200 C and T = 180 C

D) T = 180 C and T = 160 C

Use the following to answer question 8: Two bars, A and B, each of length 2.0 m and cross sectional area 1.0 m , are placed end to end as shown in the figure.2

Their thermal conductivities are k = 339 J/(s m K) and k = 837 J/(s m K). The leftA B

end of bar A is maintained at 373 K while the right end of B is maintained at 273 K. 8. What is the rate of heat transfer through this combination?

Page 2

A) 3.0 10 J/s

3

B) 6.0 10 J/s

3

C) 9.0 10 J/s

3

D) 1.2 10 J/s

4

9. The thermal conductivity of a metal decreases when temperature increases because at higher temperature A) the number of free electrons increases. B) the mean free path of electrons decreases. C) the mean speed of electrons increases. D) the mean speed of electrons decreases. 10. Complete the following statement: The absolute temperature of an ideal gas is directly proportional to A) the number of molecules in the sample. B) the average momentum of a molecule of the gas. C) the average translational kinetic energy of the gas. D) the amount of heat required to raise the temperature of the gas by 1 C. 11. Which one of the following factors is directly responsible for the pressure exerted by a confined gas? A) the atomic mass of the gas B) the density of the sample of molecules C) the temperature of the sample of molecules D) the collision of gas molecules with the sides of the containing vessel 12. When the gas enclosed beneath the piston shown in the figure receives 1930 J of heat, Q, from its surroundings, it performs 2250 J of work in raising the piston. What is the change in the internal energy of the gas?

A) 320 J

B) +320 J C) 4180 J

D) +4180 J5

13. A system containing an ideal gas at a constant pressure of 1.22 10 Pa gains 2140 J of heat. During the process, the internal energy of the system increases by 2320 J. What is the change in volume of the gas? A) +1.48 103

m

3

B) 1.48 10

3

m

3

C) +3.66 10

3

m

3

D) 3.66 10

3

m

3

Page 3

Use the following to answer question 14: 5.00 kg of liquid water is heated to 100.0 C in a closed system. At this temperature, the density 3 5 of liquid water is 958 kg/m . The pressure is maintained at atmospheric pressure of 1.01 10 Pa. A moveable piston of negligible weight rests on the surface of the water. The water is then converted to steam by adding an additional amount of heat to the system. When all of the water 3 is converted, the final volume of the steam is 8.50 m . The latent heat of vaporization of water is 6 2.26 10 J/kg.

14. What is the increase in the internal energy in the process of converting all of the water into steam? 7 7 5 6 A) 1.13 10 J B) 1.04 10 J C) 4.52 10 J D) 3.78 10 J 15. Which one of the following statements concerning a collection of gas molecules at a certain temperature is true? A) All molecules move with the same velocity. B) Most of the molecules have the same kinetic energy. C) The lower the temperature, the greater are the molecular speeds. D) The molecules have a range of kinetic energies. 16. Consider two ideal gases, A and B, at the same temperature. The rms speed of the molecules of gas A is twice that of gas B. How does the molecular mass of A compare to that of B? A) It is twice that of B. C) It is four times that of B. B) It is one half that of B. D) It is one fourth that of B. 17. Which one of the following statements concerning electrostatic situations is false?

Page 4

A) B) C) D)

E is zero everywhere inside a conductor. Equipotential surfaces are always perpendicular to E. It takes zero work to move a charge along an equipotential surface. No force acts on the charge as it is moved along an equipotential surface.

18. Complete the following statement: The internal energy of an ideal monatomic gas is A) proportional to the pressure and inversely proportional to the volume of the gas. B) independent of the number of moles of the gas. C) proportional to the absolute temperature of the gas. D) dependent on both the pressure and the temperature of the gas. 19. A mixture of two ideal gases A and B is in thermal equilibrium at 600 K. A molecule of A has one-fourth the mass of a molecule of B and the rms speed of molecules of A is 400 m/s. Determine the rms speed of molecules of B. A) 100 m/s B) 200 m/s C) 400 m/s D) 800 m/s 20. A fixed amount of ideal gas is compressed adiabatically. Which entry in the table below correctly depicts the sign of the work done, the change in the internal energy, and the heat exchanged with the environment? work done change in internal energy heat exchanged A) positive negative zero B) negative zero positive C) negative negative zero D) negative positive zero 21. An ideal gas is taken from state A to state B through process shown on the pressurevolume graph. How much heat is added to the gas in this process?

A) zero joules

B) 1.0 10 J C) 2.4 10 J D) 6.0 10 J

4

4

4

Page 5

Use the following to answer question 22: 2.0 moles of an ideal gas have an initial Kelvin temperature T and absolute pressure P . The gaso o

undergoes a reversible isothermal compression from an initial volume V to a final volume V /2.o o

22. How much heat is exchanged with the environment? If heat is exchanged, is it absorbed or released? A) P V ln 2, released C) P V /2, releasedo o o o o o o o

B) P V ln 2, absorbed

D) P V /2, absorbed

23. The ratio of the molar specific heat capacity at constant pressure to that at constant volume, , for diatomic hydrogen gas is 7/5. In an adiabatic compression, the gas, originally at atmospheric pressure, is compressed from an original volume of 0.30 m to 3 0.15 m . What is the final pressure of the gas? 5 5 5 5 A) 2.0 10 Pa B) 2.7 10 Pa C) 3.0 10 Pa D) 3.7 10 Pa 24. Which one of the following statements is true concerning the ratio of the molar heat capacities C /C for an ideal gas?p v 3

A) The ratio is always 1. B) The ratio is always less than 1.

C) The ratio is always greater than 1. D) The ratio is sometimes less than 1.

25. A quantity of carbon monoxide gas is slowly adiabatically compressed in an insulated container to one-half of its initial volume. The ratio of the specific heat capacities at constant pressure and constant volume, c /c , for carbon dioxide is approximately 1.3.P V

Determine the final pressure of the gas if the initial pressure is 2.0 10 Pa. A) 2.0 10 Pa B) 2.6 10 Pa C) 3.7 10 Pa D) 4.9 10 Pa 26. In an isothermal process, 2.33 moles of an ideal gas is compressed to one-fifth of its initial volume at 285 K. What quantity of heat is added to, or removed from, the system during this process? A) 8880 J removed B) 3020 J added C) 1070 J removed D) 6050 J removed5 5 5 5

5

Page 6

Use the following to answer question 27: An ideal monatomic gas expands isobarically from state A to state B. It is then compressed isothermally from state B to state C and finally cooled at constant volume until it returns to its initial state A.

27. How much work is done by the gas in expanding isobarically from A to B? 3 3 3 3 A) 1 10 J B) 2 10 J C) 3 10 J D) 4 10 J 28. Four point charges, each of the same magnitude, with varying signs are arranged at the corners of a square as shown. Which of the arrows labeled A, B, C, and D gives the correct direction of the net force that acts on the charge at the upper right corner?

A) A B) B

C) C

D) D

Page 7

29. Two positive point charges Q and 2Q are separated by a distance R. If the charge Q experiences a force of magnitude F when the separation is R, what is the magnitude of the force on the charge 2Q when the separation is 2R ? A) F/4 B) F/2 C) F D) 2F 30. Determine the ratio of the electrostatic force to the gravitational force between a proton -12 and an electron, F /F . Note: Permittivity of vacuum = 8.85 10 F/m ; G = 6.672 E G

10

11

Nm /kg ; m = 9.109 10e 23

2

2

31

kg; and m = 1.672 10p 31

27

kg.39

A) 1.24 10

B) 2.52 10

29

C) 1.15 10

D) 2.27 10

31. Three identical point charges, Q, are placed at the vertices of an equilateral triangle as shown in the figure. The length of each side of the triangle is d. Determine the magnitude and direction of the total electrostatic force on the charge at the top of the triangle.

A)Q2 3 , directed upward 4 0 d 2

B)Q2 3 , directed downward 4 0 d 2

C) Q2 , directed upward 2 0 d 2 D) Q2 , directed downward 2 0 d 2

32. Which one of the following statements is true concerning the the electric field strength at a point in space? A) It is a measure of the total charge on the object. B) It is a measure of the electric force on any charged object.

Page 8

C) It is a measure of the ratio of the charge on an object to its mass. D) It is a measure of the electric force per unit positive charge. 33. At which point (or points) is the electric field zero N/C for the two point charges shown on the x axis?

A) B) C) D)

The electric field is never zero in the vicinity of these charges. The electric field is zero somewhere on the x axis to the left of the +4q charge. The electric field is zero somewhere on the x axis to the right of the 2q charge. The electric field is zero somewhere on the x axis between the two charges, but this point is nearer to the 2q charge.

34. An electron traveling horizontally enters a region where a uniform electric field is directed upward. What is the direction of the force exerted on the electron once it has entered the field?

A) to the left B) to the right

C) upward6

D) downward8

35. A small sphere of mass 1.0 10 kg carries a total charge of 2.0 10 C. The sphere hangs from a silk thread between two large parallel conducting plates. The excess charge on each plate is equal in magnitude, but opposite in sign. If the thread makes an angle of 30 with the positive plate as shown, what is the magnitude of the charge density on each plate?

A) 2.5 10

9

C/m

2

B) 5.2 10

9

C/m

2

C) 1.0 10

9

C/m

2

D) 2.1 10

8

C/m

2

Page 9

36. Two point charges are arranged along the x axis as shown in the figure. At which of the following values of x is the electric potential equal to zero?

A) +0.05 m B) +0.29 m C) +0.40 m D) +0.54 m

Use the following to answer question 37: Two point charges are held at the corners of a rectangle as shown in the figure. The lengths of sides of the rectangle are 0.050 m and 0.150 m. Assume that the electric potential is defined to be zero at infinity.

37. Determine the electric potential at corner A. 4 5 5 5 A) +6.0 10 V B) 2.4 10 V C) +4.6 10 V D) 7.8 10 V Use the following to answer question 38: Two charges of opposite sign and equal magnitude Q = 2.0 C are held 2.0 m apart as shown in the figure.

38. How much work is required to move a 1.0 C charge from infinity to the point P? 9 9 9 A) zero joules B) 2.2 10 J C) 4.5 10 J D) 9.0 10 JPage 10

Use the following to answer question 39: An isolated system consists of two conducting spheres A and B. Sphere A has five times the radius of sphere B. Initially, the spheres are given equal amounts of positive charge and are isolated from each other. The two spheres are then connected by a conducting wire. 39. Determine the ratio of the charge on sphere A to that on sphere B, q /q , after theA B

spheres are connected by the wire. A) 1 B) 1/5 C) 5 D) 25 40. Which one of the following properties of a gas is not consistent with kinetic theory? A) The average speed of the gas molecules is smaller at high temperatures. B) Gas molecules make elastic collisions with the walls of the containing vessel. C) The intermolecular forces is negligible D) Gas molecules move rapidly in a random fashion.

Page 11

Answer Key -- Description 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. B C D D B A C D B C D A B B D D D C B D C A B C D A D B A D A D C D A B A A C A

Page 12