42. Tension is maintained in a string as in the figure. The observed wave speed is v = 24 m/s when the suspended mass is m = 3 kg. What is the wave speed when the suspended mass is m = 1 kg? (Gravitational acceleration g = 10 m/s² )

(A) 4.6 m/s
(B) 5.7 m/s
(C) 8.0 m/s
(D) 11.3 m/s
(E) 13.9 m/s

38. A 1 kg copper block and a 6 kg steel block are connected by a light string over a frictionless pulley. The two blocks are allowed to move on a fixed steel block wedge (θ = 60°) as shown in the figure. If the coefficients of friction of the copper-steel and steel-steel are 0.4 and 0.6, respectively, what is the acceleration of the two blocks? (Gravitational acceleration g = 10 m/s2 )(A) 5.28 m/s2 (B) 5.08 m/s2 (C) 4.88 m/s2 (D) 4.68 m/s2 (E) 4.28 m/s2

【已刪除】39. A car travels at a constant speed of 60 km/hr on a level circular turn of radius of 40 m. What is the minimum coefficient of static friction between tire and the roadway to allow the car to make the turn without sliding? (Gravitational acceleration g = 10 m/s2 ) (A) 0.83 (B) 0.73 (C) 0.63 (D) 0.53 (E) 0.43

40. A 5 kg ball is held in the hand as shown in the figure, with the arm horizontal and 40 cm from the elbow joint. The forearm mass is 2 kg and the center of gravity is 18 cm from the joint. The biceps connect to the arm at 5 cm from the joint. How much force (FM) must the biceps exert to hold the ball in place? (Gravitational acceleration g = 10 m/s2 )(A) 472 N (B) 236 N (C) 118 N (D) 59 N (E) 30 N

41. If middle C (262 Hz) and C# (277 Hz) are played together, it would cause interference beats. What the beat frequency would be if each is played one octave lower (each frequency reduced by a factor of 2)? (A) 30 Hz (B) 15 Hz (C) 7.5 Hz (D) 3.75 Hz (E) None of the above.

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

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

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