50. Suppose that 1 mole of an ideal gas undergoes a free expansion to three times its initial volume.What is the change of entropy? (The universal gas constant is R.)
(A) 2R ln 2
(B) R ln 2
(C) R ln 3
(D) R ln 4
(E) 2R ln 4

46. Sound pressure level is defined as SPL(dB) = (P⁄P0), where P is sound wave pressureand P0 = 20 μPa. SPL decreases 6 dB as a listener's distance doubles from the sound source. Thesound level is 110 dB at one meter away from the explosion of firecrackers. How far away wouldit be needed to reduce the sound level to an acceptable level of 80 decibels?(A) 5 m (B) 16 m (C) 32 m (D) 60 m (E) 100 m

47. A 5.0 L gas tank holds 1.7 mole of monoatomic helium (He) and 1.1 mole of diatomic oxygen (O2), at a temperature of 260 K. The atomic masses of helium and oxygen are 4.0 g/mol and 16.0 g/mol, respectively. What is the ratio of the root-mean-square (thermal) speed of helium to that of oxygen?(A) 1.4 (B) 2.0 (C) 2.8 (D) 4.0 (E) 5.6

48. A piece of thin uniform wire of mass m and length 3b is bent into an equilateral triangle. Find the moment of inertia of the wire triangle about an axis perpendicular to the plane of the triangle and passing through one of its vertices.(A)(B) (C) (D)(E)

49. One way to measure blood flow when blood vessels are exposed during surgery is to use anelectromagnetic flowmeter. The device surrounds the blood vessel with an electromagnet tocreate a magnetic field perpendicular to the blood flow. Since blood is a modest conductor, amotional emf develops across the blood vessel. Given the vessel diameter d, magnetic field B,and voltage V measured across the vessel, what is the volume flow rate of blood?(A) πdV⁄(4B) (B) πdV⁄(2B) (C) πdV⁄B (D) 2πdV⁄B (E) 4πdV⁄B

51. A proton of mass m and charge q is in uniform circular motion perpendicular to a magnetic fieldB . The radius of the circle is r. What is the speed of the proton?(A) qBr/3m (B) 2qBr2/(2m(r + 1)) (C) qBr2/(2m(r + 1))(D) qBr/2m (E) qBr/m

52. During each heartbeat, approximately 70 cm3 of blood is pushed from the heart at the mean arterial pressure of 100 mmHg. By assuming 72 beats per minute, what is the amount of external power output of the heart?(A) less than 0.20 W (B) 0.50 W (C) 0.84 W(D) 1.1 W (E) larger than 5.0 W

53. A square 10-turn coil with edge-length 50 cm carries a current of 2 A. ft lies in the xy plane with magnetic moment in the z direction. ft is placed in a uniform magnetic field (T). What is the magnetic potential energy of the coil in the magnetic field?(A) -2 Joule (B) -1.5 Joule (C) 1.5 Joule (D) 2 Joule (E) 2.4 Joule

54. An observer on the Earth measures the speed of spacecraft A to be 0.50c and the speed of spacecraft B to be -0.40c. What is the velocity of spacecraft B as observed by the crew on spacecraft A? (Here c is thespeed of light. The Lorentz velocity transformation is )(A) -c/6 (B) -3c/5 (C) -2c/5 (D) -c/4 (E) -3c/4

55. Two sources of light illuminate a double slit simultaneously. One has wavelength 570 nm and the second has an unknown wavelength. The fifth bright fringe (m=5) of the unknown wavelength overlaps the forth bright fringe (m=4) of the light of 570 nm wavelength. What is the unknown wavelength?(A) 326 nm (B) 380 nm (C) 456 nm (D) 512 nm (E) 713 nm

56. A family member is ready to have a brain scan using technetium-99*, an excited isotope with 6.0-hour half-life. The hospital makes this short-lived Tc-99* from the decay of molybdenum-99 then delivers it to the nuclear medicine department. After production of Tc-99*, the hospital staff takes 90 minutes to transport it to the operating room. What is an appropriate amount of Tc-99* to be produced by the technician-in-charge for the medical requirement of 10 mg of Tc-99*?(A) 10 mg (B) 12 mg (C) 16 mg (D) 20 mg (E) 24 mg