55. If the five lenses shown below are made of the same material, which lens has the shortest positive focal length?
(A)
(B)
(C)
(D)
(E)

51. The diagram shows a U-tube having cross-sectional area A and partially filled with oil of density . A solid cylinder, which fits the tube tightly but can slide without friction, is placed in the right arm. The system reaches equilibrium. The weight of the cylinder is: (A) ALρg (B) L 3 ρg (C) Aρ(L + h)g (D) Aρ(L – h)g (E) None of the above.

52. A solid brass ball of mass 0.280 g will roll smoothly along a loop-the-loop track when released from rest along the straight section. The circular loop has radius R = 14.0 cm, and the ball has radius r << R. What is h if the ball is on the verge of leaving the track when it reaches the top of the loop? (A) 47.8 cm (B) 27.8 cm (C) 57.8 cm (D) 37.8 cm (E) 78.3 cm

53. The emf E = 1.2 kV, C = 6.5 μF, R1 = R2 = R3 = 0.73 MΩ. With C completely uncharged, switch S is suddenly closed (at t = 0). At t = 0, what is current i1 in resistor R1? (A) 3.3✖10-3 A (B) 3.3✖10-4 A (C) 1.1✖10-4 A (D) 1.1✖10-3 A (E) 2.2✖10-3 A

54. The following shows a rod of length L = 10.0 cm that is forced to move at constant speed v = 5.00 m/s along horizontal rails. The rod, rails, and connecting strip at the right form a conducting loop. The rod has resistance 0.400 Ω; the rest of the loop has negligible resistance. A current i = 100 A through the long straight wire at distance a = 10.0 mm from the loop sets up a (nonuniform) magnetic field through the loop. Find the emf. (μ0 = 4π10-7 T  m/A, ln 2 = 0.693, ln 10 = 2.303, ln 11 = 2.398) (A) 2.4✖10-4 V (B) 5.8✖10-3 V (C) 4.8✖10-5 V (D) 3.9✖10-4 V (E) 8.8✖10-4 V

56. For quantum model, E = hν = hc / λ, where E is photon energy in unit of eV, h is the Planck’s constant ( ), ν is the frequency (s -1 ), λ is the wavelength in meters (m), then E✖λ (eV m) is: (A)  1.24 ✖10- 3 (B)  1.24✖ 10- 4 (C) 1.24 ✖10-5 (D)  1.24✖ 10- 6 (E)  1.24✖ 10-7

57. A particle with mass m and charge q, moving with a velocity v, enters a region of uniform magnetic field B, as shown in the figure below. The particle strikes the wall at a distance d from the entrance slit. If the particle’s velocity stays the same but its charge-to-mass ratio is doubled, at what distance from the entrance slit will the particle strike the wall? (A) 2d (B) (C) d (D) (E)

58. The position of a particle moving on x-axis is given by  x = , with x in meters and t in seconds. Which statement in the following is correct? (A) The particle is moving in the positive direction of x with a speed of 1.5m/s at t =1.0 s. (B) The acceleration of the particle at t = 1.0 s is -0.50 m / s 2 . (C) The acceleration of the particle is constant. (D) The particle is moving in the negative direction of x with a speed of 0.50m/s at t =1.0 s. (E) The velocity of the particle is constant.

59. A wire loop of area 1000 cm 2 has a resistance of 10 ohms. A magnetic field B normal to the loop initially has a magnitude of 0.1 T and is reduce to zero at a uniform rate in 10-4 s. Thus, the resulting current is: (A) 10000 A (B) 1000 A (C) 100 A (D) 10 A (E) 1 A

60. A rod of semiconducting material with length L and cross-sectional area A lies along the x-axis between x = 0 and x = L . Its resistivity varies with x according to . The material obeys Ohm’s Law. What is the total resistance of the rod? (A)(B)(C)(D) (E)

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