2. Which of the following statements help(s) to explain why gas can fill the vessel containing it completely while liquid cannot?

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1 Name: Class: ( ) There are 30 questions. Time Allowed: 45 min 1. Kinetic theory explains the behaviour of a substance in terms of the behaviour of the molecules in it. Which of the following is/are the property(properties) of an individual molecule? (1) Momentum. (2) Specific heat capacity. (3) Temperature A. (1) only B. (2) only C. (3) only D. (1) and (3) E. (1), (2) and (3) 2. Which of the following statements help(s) to explain why gas can fill the vessel containing it completely while liquid cannot? (1) Gas molecules move freely in random directions. (2) Negligible intermolecular force exists between gas molecules. (3) Gas molecules exert pressure on the vessel. A. (1) only B. (2) only C. (3) only D. (1) and (2) E. (2) and (3) 3. A fixed mass of gas is heated under a constant volume, which of the following statements is/are correct? (1) The average distance between the gas molecules increases. (2) The gas molecules move with a greater average speed. (3) The average collision frequency between the molecules and the container walls increases. A. (1) only B. (2) only C. (3) only 4. A gas of fixed mass is kept inside an air tight cylinder as shown in the figure below. The piston is smooth and is held in equilibrium by the atmospheric pressure and the gas pressure. If the temperature of the gas is increased, the piston moves to the left and stops at a new position. Which of the following statements is/are correct? (1) The new gas pressure is greater than the atmospheric pressure. (2) The average speed of the gas molecules increases. (3) The average number of collisions per second between the molecules and the piston increases. A. (2) only B. (3) only C. (1) and (2) only 5. A sprayer contains a compressed gas at 30 o C and a pressure of 2.5 atmospheres. Find the temperature at which the sprayer explodes if the maximum tolerable gas pressure of the container is 3.0 atmospheres. The volume of the container is a constant. A. 36 o C B. 60 o C C. 75 o C D o C E. 364 o C

2 6. An uniform capillary tube traps an air column by a mercury thread as shown in the figure below. The air column has a length of 10 cm when the water bath is at 20 o C. What will be the length of the water is at 80 o C? A. 8.3 cm B. 12 cm C cm D. 40 cm E. Cannot be determined because the diameter of the air column is not given. 7. A column of air is trapped above oil in a glass tube as shown in the figure below. The readings of the pressure (P) and length of air column (L) at constant temperature are plotted on a graph. Which of the following graphs most probably represents their relationship? A. B. C. D.

3 8. A student performed an experiment on the pressure law. He plotted the readings of pressure and temperature on a graph and got a line as shown below. What is the absolute zero in Celsius deduced from this graph? A o C B o C C o C D o C E o C 9. A gas column is trapped by a mercury thread inside a capillary tube as shown below. The length of the gas column is 8 cm and 12 cm in position (A) and (B) respectively. If the atmospheric pressure is 1 10 Nm, find the gas pressure in position (A). A Nm B Nm C Nm D Nm E Nm A vessel of volume 1 10 m contains 0.72 g of an ideal gas at a pressure of 1 10 Pa. The r.m.s. velocity of the gas molecules is A. 20 m s -1 B. 110 m s -1 C. 340 m s -1 D. 650 m s -1 E m s The root-mean-square speed of a sample of helium gas molecules, each of mass m, is c. Which of the following deductions is correct? A. The percentage of molecules travelling at speed c is greater than at other speeds. B. Half of the molecules travel at a speed higher than c. C. All molecules travel randomly with speed c. D. The average speed of the molecules is c. 1 2 E. The average kinetic energy of the molecules is 2 mc.

4 12. A gas in a container with a smooth piston is heated at constant pressure so that it occupies a different volume. A force is then applied to the piston to restore the volume to its original value a constant temperature. Which of the following V-T graphs best represents the above procedures? A. B. C. D. 13. A radioactive source is tested as follows: Absorber placed between source and GM counter (1) Thin aluminium foil (0.2 mm) (2) Thin lead sheet (2 mm) (3) Thick lead sheet (20 mm) Effect on count rate Fall significantly. No significant difference with (1) Falls below that in (1) What type(s) of radiation does the source emit? A. α only B. β only C. γ only D. α and γ E. α and β 14. A counter is placed near a very weak radioactive source which has a half-life of 1 hour. The counter registers 100 counts/min at noon and 80 counts/min at 1 p.m. The expected count rate, in counts/min, at 3 p.m. on the same day is A. 40 B. 50 C. 55 D. 60 E Ra is one of the nuclides in the uranium decay series. If the stable end-product of this series is Pb, the number of β -particles emitted between the 226 Ra stage and the end of the series is 82 A. 4 B. 6 C. 10 D. 14 E Protactinium extracted from a solution of uranyl nitrate decays with a half life of 72 s. The value of its decay constant is A s B s D s E s C s 1

5 Ra decays to Rn with a half-life of 1600 years. Which of the following statements is/are correct? 86 (1) α particle is produced in the decay. (2) All 226 Ra has decayed after 3200 years. (3) The half-lfie of 226 Ra can be shortened by heating. A. (1) only B. (3) only C. (1) and (2) 18. When alpha particles are fired in a beam at a thin sheet of gold, they are scattered through a wide rage of angles, from zero to 180 o from the incident beam. This experiment shows that the gold atom has (1) electrons in different orbits. (2) a volume consisting mainly of empty space. (3) a small, dense, charged nucleus. A. (1) only B. (3) only C. (1) and (2) 19. Given: mass of proton = u mass of neutron = u mass of 206 Pb = u 1 u corresponds to 931 MeV 82 Find the binding energy per nucleon for a 206 Pb nucleus. 82 A MeV B MeV C MeV D MeV E MeV 20. Which of the following statements about a typical nuclear reactor in a power plant is/are correct? (1) The percentage of 235 U isotope in fuel rods is higher than that in natural uranium. (2) Boron-coated steel rods are used to control the rate of neutron production. (3) Pressurized water is used as coolant inside the reactor core. A. (1) only B. (3) only C. (1) and (2) 21. The linear attenuation coefficient of a medium for X-rays is 6 m -1. Which of the following statements is true? A. Each meter of the medium absorbs six units of X-ray energy. B. Each meter of the medium absorbs six X-ray photons. C. Each meter of the medium reduces the intensity of X-ray to 50%. D. The intensity of X-ray is reduced to 50% by the medium of thickness about 11.6 cm. 22. As a beam of X-ray passes through a medium, which of the following will decrease? (1) the amplitude of X-ray (2) the energy of the photons (3) the frequency of X-ray 23. In an X-ray film, (1) a dark region represents the body part absorbing little amount of X-ray. (2) the image contrast is caused by the difference in attenuation of X-rays. (3) a slice of the body structure is shown.

6 24. Which of the following statements about ultrasound imaging and X-ray imaging is/are true? (1) Both use pulse-echo technique. (2) Both involve the use of waves to probe inside the body of a patient. (3) One detects the reflected beam and the other detects the transmitted beam. 25. In a CT scan, the following equation is involved: ( ) 1 2 I I e µ µ µ x N = 0. Which of the following statements is/are true? (1) The value of x depends on the size of the organ to be imaged. (2) The computer program is designed to find the values of µ, µ,, µ. 1 2 N (3) The value of I is measured by an X-ray detector. 26. Which of the following statements about computed tomography (CT) is NOT true? A. CT is based on the fact that different body structures have different linear attenuation coefficients. B. The overall attenuation along a scan line is related to the sum of the linear attenuation coefficients of the voxels on the scan line. C. The number of equations to be solved is not less than the total number of voxels in a CT slice. D. The variables in the equations are the densities of the voxels. 27. The half-lives of a tracer due to physical process and biological process are 5 hours and 4 hours respectively. What is the effective half-life of the tracer? A hr B. 2.2 hr C. 3 hr D. 4.5 hr 28. Radionuclide imaging (1) measures the functions of an organ. (2) provides detail view of internal organs. (3) gives clear and sharp image. 29. The SI unit of effective dose is A. joule B. sievert C. gray D. becquerel 30. Which of the following statements about a hot spot in radionuclide imaging is/are true? (1) A hot spot indicates too much uptake of the tracer. (2) A hot spot reveals that the function of an organ may be abnormal. (3) A hot spot shows that the density of the organ is higher than elsewhere. END OF SECTION A