4. A rod of length L and mass M is placed along the x-axis with one end at the origin, as shown in the figure below. The rod has linear mass density , where x is the distance from the origin. Which of the following gives the x-coordinate of the rod’s center of mass?
(A)
(B)
(C)
(D)
(E)

沒有 【段考】國二理化下學期 權限，請先開通．

1. The capacitance of a cylindrical capacitor can be increased by: (A) decreasing both the radius of the inner cylinder and the length. (B) increasing both the radius inner cylinder and the length. (C) increasing the radius outer cylindrical shell and decreasing the length. (D) decreasing the radius inner cylinder and increasing the radius of the outer cylindrical shell. (E) only by decreasing the length.

2.A layer of oil with density 800 kg/m 3 floats on top of a volume of water with density 1,000 kg/m 3 . A block floats at the oil-water interface with 1/4 of its volume in oil and 3/4 of its volume in water, as shown in the figure below. What is the density of the block ? (A) 200 kg/m3 (B) 850 kg/m3 (C) 950 kg/m3 (D) 1,050 kg/m3 (E) 1,800 kg/m3 

3. X rays of wavelength λ= 0.250 nm are incident on the face of a crystal at angle θ, measured from the crystal surface. The smallest angle that yields an intense reflected beam is θ = 14.5°. Which of the following gives the value of the interplanar spacing d? ( sin 14.5° 1/4 )(A)0.125 nm (B) 0.250 nm (C) 0.500 nm (D) 0.625 nm (E) 0.750 nm

【已刪除】 5. A long, straight, hollow cylindrical wire with an inner radius R and an outer radius 2R carries a uniform current density. Which of the following graphs best represents the magnitude of the magnetic field as a function of the distance from the center of the wire? (A) (B) (C) (D) (E)送分.

6. The density of ice is 0.920 g/cm3 while that of sea water is 1.025 g/cm3 . What fraction of an iceberg is submerged?(A)0.898(B)0.927 (C) 0.976 (D) 1.087 (E) 1.114

 7. A series RLC circuit, driven with a sinusoidal external emf with rms voltage 120 V, contains a resistance R = 200 Ω, an inductance L =1.0 H , and a capacitance C = 16 μF. What is the resonance frequency of this circuit? (A) 960 Hz (B) 1,600 Hz (C) 40 Hz (D) 6,400 Hz (E) 250 Hz

8. A star radiates uniformly in all directions. At a distance of 5.0 ✖ 1012 m from the star, the intensity of the radiation from the star is 15 W / m2 . What is the total power output of the star? (A)   3.2✖1038W (B) 4.7✖10 27W  (C)  3.8✖1026 W(D)  7.5✖1013W  (E)   1.1✖1015W

9. The focal length of a camera lens is 20.0 cm. How far from the lens should the subject for the photo be if the lens is 20.5 cm from the film? (A) 8.20 m (B)4.10 m (C) 2.10 m (D) 6.30 m (E) 10.0 m

 10. Two different samples have the same mass and temperature. Equal quantities of energy are absorbed as heat by each. Their final temperatures may be different because the samples have different: (A) thermal conductivities (B) coefficients of expansion (C) densities (D) volumes (E) heat capacities