12.A block with mass m 250g is fastened to a spring with spring constant k 85N/m. The system is excited to oscillate. Assume that there is a velocity-dependent damping force F_d -bv in the system with b 70g/s. How long does it take for the amplitude of the damped oscillation to drop to half its initial value? (ln2 0.693)
(A)3s
(B)4s
(C)5s
(D)6s
(E)7s

8.Some sunglasses are coated on one side with a thin film of MgF2 to reduce reflection from the glass surface. The index of refraction of MgF2 is 1.38; that of the glass is 1.50. What is the least coating thickness that eliminates (via interference) the reflections in the range of the visible spectrum (≒ 550nm)? Assume that the light is approximately perpendicular to the glass surface. (A)40nm (B)60nm (C)80nm (D)100nm (E)120nm

9.The two headlights of a car are 1.4m apart. At what maximum distance will the eyes resolve them? Assume that the pupil diameter is 5.0mm, and use a wavelength of 550 nm for the light. (Consider only diffraction effects.) (A)3km (B)5km (C)10km (D)15km (E)20km Fig 1

10.A flute (which we treat as a pipe open at both ends) is 60cm long. How far from the mouthpiece should a hole be uncovered for the fundamental frequency to be 330Hz? (The speed of sound is 330m/s). (A)35cm (B)40cm (C)45cm (D)50cm (E)55cm

11.An ideal monatomic gas undergoes a quasistatic expansion to one-third of its initial pressure. Find the ratio of the final volume to the initial volume if the process is adiabatic. (0 = Cp / Cv 5/3 for ideal monatomic gas, log3 0.5) (A) (B)100.3 (C)100.5 (D)100.6 (E)100.7

13.A thin rod whose length L is 10cm and whose mass m is 100g, suspended at its midpoint from a long wire. Its period Ta of angular SHM (Simple Harmonic Motion) is measured to be 2.50 s. An irregularly shaped object is then hung from the same wire and its period Tb is found to be 5.0s. What is the rotational inertia of the irregular object about its suspension axis? (The rotational inertia for a rod is  mL2  ) (A) (B) (C) (D) (E)

14.In high-speed motion through air, the resisting force is approximately  F = cv2 . For a human body falling through air in a spread-eagle position, c is about 0.25kg/m. An 80kg sky diver jumps out of an airplane and reaches terminal speed before opening the parachute. What is the terminal speed? (A)49m/s (B)56m/s (C)72m/s (D)84m/s (E)98m/s

15.A neutral water molecule (H2O) in its vapor state has an electric dipole moment of magnitude  6.2 ́ 10Cm. How far apart are the molecule’s center of positive and negative charge? (A)1.9pm (B)2.9pm (C)3.9pm (D)4.9pm (E)5.9pm .

16.In a mass spectrometer, the initally stationary ion is accelerated by the electric field due to a potential V. The ion enters a separator chamber in which a uniform magnetic field B is perpendicular to the path of the ion. The magnetic field causes the ion to move in a semicircle, striking a photographic plate at distance x from the entry slit. Suppose that B 80mT and V 1000 Volts, and ion of charge q +1.60 ́ C strikes the plate at x 1.63m, what is the mass of the ion? (A)185.7u (B)204.9u (C)224.6u (D)241.5u (E)267.8u

17.Consider a parallel-plate capacitor of plate area A and plate separation. A potential difference Vo is applied between the plates. The battery is then disconnected, and a dielectric slab of thickness b and dielectric constant k is placed between the plates. Assuming A 100cm2 , d 1.00cm, Vo 90V, b 0.8cm, k 2.00. What is the capacitance with the slab in place? ( ) (A)14.8pF (B)16.8pF (C)17.9pF (D)20.9pF (E)21.9pF 

18.A 200g top spinning at 20 rev/s makes an angle of 30° to the vertical and precesses at a rate of 1 rev per 10.0s. If its CM (Center of Mass) is 4.0cm from its tip along its symmetry axis, what is the moment of inertia of the top? (A) (B) (C) (D) (E)