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

34. A police crime lab is trying to determine whether someone was murdered or died as a result of an accident. The victim was struck in the temple by a 4 kg sculpture that is alleged to have fallen off a bookcase. The sculpture presumably fell a distance of 20 m and the corner that struck him had an area of 0.25 cm2 . If the time for the sculpture to stop was 1 ms, the pressure on his temple, in N/m2 , was ______. (Gravitational acceleration g = 10 m/s2 ) (A) 3.2 × 105 (B) 1.6 × 106 (C) 3.2 × 106 (D) 1.6 × 109 (E) 3.2 × 109

35. A 3 kg particle moves to the right at 4 m/s as shown in the figure. The magnitude of its angular momentum in (kg ● m2 /s) about the point O is ______.  (A) 0 (B) 48 (C) 72 (D) 144 (E) 1728

36. A particle moves in the xy plane, starting from the origin at t = 0 with an initial velocity having an x component of 20 m/s and a y component of −15 m/s. The particle experiences an acceleration in the x direction, given by ax = 4 m/s2 . What is the total velocity at any time? (A)(B)(C)(D)(E)

37. A grindstone increases in an angular speed from 4 rad/s to 12 rad/s in 4 s. Through what angle does it turn during that time interval if the angular acceleration is constant? (A) 8 rad (B) 12 rad (C) 16 rad (D) 32 rad (E) 64 rad

【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.

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

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