50. A steam of water with a constant flow at 1 kg/s cools a machine. The water enters the machine at 10 °C and leaves at 80 °C. How much thermal energy is removed every minute? The specific heat capacity of water is 4.186 kJ/kg.K.
(A) 17.6 MJ
(B) 15.1 MJ
(C) 251.2 kJ
(D) 25.1 kJ
(E) 2.5 MJ

46. The sound intensity level is defined as L = 10-log10(1/10) with the unit dB, where I is the sound intensity in units of W/m² and I0 = W/m². If a machine generates a noise level of 84 dB, what will be the noise level if an additional identical machine is turned on? [ = 0.301] (A) 84 dB (B) 168 dB (C) 90 dB (D) 190 dB (E) 87 dB

47. Two stars of masses M and 2M are in a binary star system, orbiting a common center of mass. Which of the following statements is true about their orbital periods? (A) The star with mass Mhas a longer orbital period. (B) The star with mass 2M has a longer orbital period. (C) Both stars have the same orbital period. (D) The orbital periods depend on the distance between the stars. (E) The orbital periods are independent of the masses of the stars.

48. A sample of gas is held in a container at a constant pressure. If the volume is halved, how will the rms (root-mean-square)-speed of the molecules change compared with the original rms-speed? (A) √2 times smaller (B) √2 times greater (C) the same (D) 2 times greater (E) 2 times smaller

49. A person with a volume of 0.08 m³ floats in fresh water (density = 1000 kg/m³). What is the buoyant force acting on the person? (Assume the acceleration due to gravity g is 10 m/s²) (A) 8000 N (B) 800 N (C) 80 N (D) 8 N (E) 0 N

51. A hot object at temperature 500 K is moved to contact with a cool object at 300 K, and a heat of 50 kJ flows irreversibly from one to the other. Assume that neighter object changes its temperature. How much is the entropy of the universe changed? (A) 1000 J/K (B) 40 MJ/K (C) 66.7 J/K (D) 62.5 J/K (E) none of the above

52. The Figure shows a planet moving about the sun in an elliptical orbit. Its speeds at the following four points shown in the Figure are , repsectively. Which of the following statement is correct? (A)(B)(C)(D)(E) none of the above

53. A patient is undergoing radiation therapy. A radioactive isotope decays and emits an a particle with an initial velocity of 2×107 m/s. The a particle is slowed down by the Coulomb force from a nearby nucleus, experiencing a deceleration of 5× m/s². How far will the a particle travel before coming to a stop? (A) 0.1 meters (B) 0.2 meters (C) 0.3 meters (D) 0.4 meters (E) 0.5 meters

54. A patient's prosthetic leg, weighing 5 kg, is sliding across the floor with a coefficient of kinetic friction of 0.2. What is the force of friction acting against the leg? (g = 9.8m/s²) (A) 9.8 N (B) 1N (C) 49 N (D) 1.96 N (E) 245 N

55. How long will it take for an oscillator at a frequncy of 2.5 Hz to make 100 vibrations? (A) 250 s (B) 40 s (C) 25 s (D) 4 s (E) 0.025 s

56. Cobalt Co Co has a half-life of 5 years. If there was sample of that isotope with an initial mass of 240 g, how much of the sample remains after 30 years? (A) 30 g (B) 15 g (C) 7.5 g (D) 3.75 g (E) 0.89 g