42. An ambulance moves at a speed of 50 km/hr, and its siren emitting sound at a frequency of 5.0x10² Hz. What frequency of sound is heard by a runner who is running at 4 m/s approaching each other in the opposite direction (the speed of sound in air is 345 m/s)?
(A) 47 Hz
(B) 475 Hz
(C) 506 Hz
(D) 527 Hz
(E) 555 Hz

38. The wing of an airplane has an area of 1 m2 , and its wing thickness is 0.5 m. Air flows over the top at 20 m/s and under the wing at 10 m/s. The density of air is 1.2 kg/m3 . What is the net force on the wing due to Bernoulli effect? (Gravitational acceleration g = 10 m/s2 ) (A) 12 N (B) 15 N (C) 18 N (D) 183 N (E) 186 N

39. A large tank of water has a hose connected to it. The tank is sealed at the top and has compressed air between the water surface and the top. When the water height h is 3.5 m the pressure of the compressed air is 4.0 x 105 Pa. Take the atmospheric pressure to be 1.0 x105 Pa. What is the speed of the water when it flows out of the hose if h is 3.5 m? (A) 30.8 m/s (B) 28.4 m/s (C) 26.8 m/s (D) 25.5 m/s (E) 23.4 m/s

40. A stainless steel container has a surface area of 0.5 m2 and thickness of 2 cm. If the container is fully filled with 57°C hot-water and the temperature in the room is 27°C, what is the rate of energy loss through the container? (The thermal conductivity of stainless steel is 80 W/m/K) (A) 30 kW (B) 60 kW (C) 120 kW (D) 180 kW (E) 210 kW

41. A jack could lift a very heavy object like a car. It compressed air and exerts a force on a small piston of area 10 cm2 and the pressure is transmitted by an incompressible liquid to a second piston of area 30 cm2 . If we want to lift a car weighting 1300 kg, what force must be exerted in the small area piston? (A) 43.3 N (B) 424.6 N (C) 433.3 N (D) 1300.0 N (E) 4247.7 N

43. One rope is wiggled with frequency f = 2.0 Hz, amplitude A = 1.0 m, and wave speed v = 4.0 m/s. What is the mathematical description of this wave? (A) y(x,t) = cosπ (2x − t) (B) y(x,t) = cosπ (2x + t) (C) y(x,t) = cosπ (x − 2t) (D) y(x,t) = cosπ (x + 2t) (E) y(x,t) = cosπ (x − 4t)

44. There is a 1 kg gallium block and its melting point is around 30°C. What is the change of entropy when it was melted from solid to liquid at 30°C? (The fusion heat of gallium is Lf = 80.18 kJ/kg) (A) 0 (B) 0.265 kJ/K (C) 0.374 kJ/K (D) 2.673 kJ/K (E) 3.779 kJ/K

45. Two charges of 15 pC and −40 pC are inside a cube with sides that are of 0.40 m length. Determine the net electric flux through the surface of the cube. (εo= 8.85 x 10-12 C2 / N•m2 ) (A) 2.8 N•m2 /C (B) −2.8 N•m2 /C (C) 1.1 N•m2 /C (D) −1.1 N•m2 /C (E) −0.47 N•m2 /C

46. A solid conducting sphere (radius = 5.0 cm) has a charge of 0.25 nC distributed uniformly on its surface. If point A is located at the center of the sphere and point B is 15 cm from the center, what is the magnitude of the electric potential difference between these two points? (ke = 9 x 109 N•m2 /C2 ) (A) 15 V (B) 23 V (C) 30 V (D) 45 V (E) 60 V

47. A segment of wire of total length 2.0 m is formed into a circular loop having 5.0 turns. If the wire carries a 1.2-A current, determine the magnitude of the magnetic field at the center of the loop. (μ0 = 4π• 10-7 T∙m/A) (A) 59 μT (B) 69 μT (C) 79 μT (D) 89 μT (E) 94 μT

48. A circuit consists of a capacitor and an inductor that are sequentially connected. If the capacitance is 0.5 mF and the inductance is1 H, what is the resonance frequency of this circuit? (A) 23.4 rad/s (B) 44.7 rad/s (C) 50.5 rad/s (D) 76.8 rad/s (E) 87.6 rad/s