47. A tuning fork is known to vibrate with frequency 262 Hz. When it is sounded along with a mandolin string, four beats are heard every second. Next, a bit of tape is put onto each tine of the tuning fork, and the tuning fork now produces five beats per second with the same mandolin string. What is the frequency of the string?
(A) 257 Hz
(B) 258 Hz
(C) 262 Hz
(D) 266 Hz
(E) 268 Hz

43. When an ambulance passes in front of an observer, the sound frequency is 440 Hz when the ambulance is approaching, and the frequency drops to 400 Hz when the ambulance is moving away. What is the speed of the ambulance? (Assume the speed of sound is 345 m/s at that time.) (A) 13.8 m/s (B) 14.0 m/s (C) 14.4 m/s (D) 15.4 m/s (E) 16.4 m/s

44. Under ambient conditions, which gas has the adiabatic ratio of molar heat capacities γ most close to 1.4? (γ = CP/CV) (A) Ar (B) CO (C) Cl2 (D) CO2 (E) CH4

【已刪除】45. A 50 m bridge is made with segments of concrete. If the linear expansion coefficient is 1.2 × 10-5 °C -1 , how much spacing is needed to allow for expansion during an extreme temperature change of150 °F? (A) 2.0 cm (B) 2.5 cm (C) 3.0 cm (D) 3.5 cm (E) 4.0 cm

46. A Carnot engine is operating at its theoretical maximum efficiency of 60%. If the waste heat has a temperature of 38 °C, what is the temperature of the boiler? (A) 94 °C (B) 225 °C (C) 350 °C (D) 504 °C (E) 775 °C

48. Determine the energy stored in C2 when C1 = 15 μF,C2 = 10 μF, C3 = 20 μF, and V0 = 18 V.(A) 1.60 mJ (B) 0.72 mJ (C) 0.50 mJ (D) 0.32 mJ (E) 0.18 mJ

49. A solid, insulating sphere of radius a has a uniform charge density throughout its volume and a total charge Q. Concentric with this sphere is an uncharged, conducting, hollow sphere whose inner and outer radii are b and c as shown in the figure. Find the magnitude of the electric field for r ＜ a. (A) (B) (C)(D) (E) E = 0

50. Two long straight current-carrying parallel wires cross the x axis and carry currents I and 3I in the same direction, as shown in the figure. At what value of x is the net magnetic field zero?(A) 1 (B) 3 (C) 4 (D) 5 (E) 7

51. A certain capacitor has a capacitance of 5 μF. After it is charged to 5 μC and isolated, the plates are brought closer together so its capacitance becomes 10 μF. The work done by the agent is about ______. (A) −1.25 × 10–6J (B) 8.3 × 10–7J (C) −8.3 × 10–7J (D) 1.25 × 10–6J (E) −3.75 × 10–6J

52. A plane with a wing length of 50 m is flying westward where the downward component of the earth’s magnetic field is 6 ✖ 10-5 T. What is the difference in potential between the wingtips when the speed of the plane is 720 km/hr, and which wingtip is positive? (A) 2.16 V, south (B) 2.16 V, north (C) 0.96 V, south (D) 0.96 V, north (E) 0.60 V, south 

53. Implanted medical devices are often charged by transcutaneous energy transfer (TET), which uses a pair of coils in close proximity for wireless charging. The change of current in the coil outside the body causes the magnetic flux of the coil inside the body to change, thus generating an induced electromotive force. There are 10 coils with a radius of 1 cm, and the current of the outer coil drops from 10 A to 0, within 6 × 10-6 s, what is the average induced electromotive force of the inner coil? (Magnetic constant μ0 is 4π ✖ 10-7 T●m/A.) (A) 2.58 V (B) 2.79 V (C) 3.05 V (D) 3.29 V (E) 3.54 V