42. At one instant, a force acts on a 0.25 kg object that has position vectorand velocity What is the object's angular momentum about the origin?
(A) -1.5 kg m²/s
(B) 1.5 kg m²/s
(C) -0.75 kg m²/s
(D) -0.375 kg m²/s
(E)0 kg m²/s

38. It takes time T for M gram(s) of a radioactive substance to decay to M /4 gram(s). How long does it take for M/4 gram(s) of the substance to decay to M /8 gram(s)? (A)2T(B)T (C)T/2(D)T2 (E)

39. A 5.0-kg ball is dropped from a cliff. Given the resistive force is R = (0.49 kg/m)v2, where v is the speed of the ball, and the gravitational acceleration is g = 9.8 m/s2, what is the terminal speed the ball? (A) 4.9 m/s (B) 10 m/s (C)40 m/s (D) 2.0 m/s (E) 20 m/s

40. In the figure, the string is tensioned by a hanging block of mass m and can vibrate with a fundamental frequency f. If one wants to create a fundamental frequency of 2f, what should the block's mass be?(A)m (B) (C)2m (D)m/2 (E)4m

41. The force  in the figure will keep the block and the pulleys in equilibrium. The block has mass m. Neglect the mass of pulleys and strings and friction in the system. What is the strength of?(A)mg (B)mg/3 (C)mg/5 (D)mg/7 (E) mg/9

43. A jet aircraft of speed 200 m/s is making a vertical circular loop of radius 2 km. What is the force exerted by the seat on the 60-kg pilot at the top of the loop? (Gravitational acceleration g = 9.8 m/s2) (A)12N(B)24 N (C)306N (D) 612 N (E) 48 N

44. Four objects are released from rest at the top of an inclined plane and roll down the plane (see the figure). A is a solid sphere. B is a hollow sphere, C is a solid cylinder, and D is a hollow cylinder. All of the four objects have identical radii and masses. Assume that the objects roll without slipping. Which one would win the race?(A) A (B) B (C) C (D) D (E) AIl arrive at the end of the inclined plane at the same time. 

45. Knowing that a particle of mass m in a potential will do a simple harmonic motion as x(t) = X cos(ωt +Φ), where x(t) is the position of the particle with time. What will be the angular frequency for a particle of mass 2m when it moves in this potential? (A)ω(B)2ω (C)ω/2(D) (E)

46. Assuming a satellite orbits a planet in a perfect circle with radius r. If the mass of the satellite is Ms and the mass of the planet is MP, what is the speed of the satellite orbiting the planet? (G is the gravitational constant.) (A)(B)(C)(D)(E)

47. If an amount of heat Q can increase the temperature of a solid metal sphere of diameter D from 10℃ to 12℃. What is the amount of heat needed to increase the temperature of a solid sphere of diameter 2D of the same metal from 100C to 16℃? (A)Q(B)3Q (C)6Q (D) 24Q (E) 48Q

48. Two opposite charges +q and -q are located as the right figure shows. What is the resulting electric field at points on the y axis?  (A)(B) (C)(D)(E)0