12. A ball of mass me is released from rest and acquires velocity of magnitude vB before hitting the ground. The ratio of the kinetic energy the Earth (mass ) acquires to the kinetic cnergy the ball acquires is m:
(A) 0.
(B)
(C)
(D) 1.
(E)

8. A 10-g bullet moving horizontally with a speed of 2.0 km/s strikes and passes through a 4.0-kg block moving with a speed of 4.0 m/s in the opposite direction on a horizontal frictionless surface. If the block is brought to rest by the collision, what is the kinetic energy of the bullet as it emerges from the block? (A)0.51 kJ (B) 0.29kJ (C) 0.80 kJ(D) 0.13 kJ(E) 20.0 kJ

9. A wheel of radius R is mounted on a frictionless, horizontal axle that is perpendicular to the wheel and passes through the center of mass of the wheel. A light cord wrapped around the wheel supports a object of mass m. If released from rest with the string taut, the object is observed to fall with a downward acceleration of 4.0 m/s2. If the moment of inertia (of the wheel) about the given axle is written as BmR2, then B=? Take g= 10 m/s. (A)1.0 (B)1.5 (C)2.0 (D)3.0 (E) 3.5

10. A merry-go-round of radius R = 2.0 m has a moment of inertia I = 250 kg-m2, and is rotating at 10 rpm. A child whose mass is 25 kg jumps onto the edge of the merry-go-round, heading directly toward the center at 6.0 m/s. The new angular speed (in rpm) of the merry-go-round is approximately (A)10(B)9.2 (C) 8.5 (D)7.1 (E)6.4

11. The figure shows a uniform rod (length L = 1.0 m, mass m = 2.0 kg) suspended from a pivot a distance d = 0.25 m above its center of mass. If the angular frequency for small oscillations is ω, then ω2 , in (rad/s)2, is approximately (Given the moment of inertia about a perpendicular axis through the center of mass is = mL2 /12 and take g = 10 m/s2) (A)1.0 (B)6.25 (C) 2.25 (D) 17.1 (E) 12.25

13. An asteroid revolves around the Sun with a perihelion 0.5 AU and an aphelion of 7.5 AU. What is its period of revolution? Knowing that lAU is the average radius of the Earth orbit around the Sun (A)4 years(B) 8 years (C) 16 years(D)32 years (E)64 years

14. A 3.0-kg block is on a horizontal surface. The block is at rest when, at t = 0, a force (magnitude P = 12 N) acting parallel to the surface is applied to the block causing it to accelerate. The coeflicient of kinetic friction between the block and the surface is 0.20. At what rate is the force P doing work on the block at t = 2.0 s? Take g = 10 m/s2.(A)54W(B)48W(C)42W(D)59 W(E) 24 W

15. Star X is 200 light-years away from the Earth. Astronauts Joe and Mary, both at age of 30, travel together to star X in a spaceship that moves with constant speed of √0.9999c. When they reach star X, what is the age of Joe observed by Mary? (A) Joe and Mary are already dead since it takes about 200 years to get there. (B) Joe is still about 30 years old since it takes less than 3 months to get there. (C) Joe is about 32 years old. (D) Joe is about 35 years old (E) Joe is 50 years old.

複選題16. A bubble having a volume of 1.00 cm3 is released from the bottom of a water tank where the depth is 10.0 m. What will the volume of the bubble be when it reaches the surface? The temperature of the water at the surface is 27.0 °C, whereas it is 57.00C at the bottorn. (The density of water is 1.00 x 103 kg/m3. Take g = 10 m/s2 and 1 atm = 1.0 x 105 Pa) (AB)1.10 cm3 (AC) 2.20 cm3(AD)1.45 cm3(AE)1.65 cm3(BC)1.35 cm3 (BD)一律送分

17. Liquid metal of mass m kg at 500 K is mixed with the same liquid metal of same mass at 1500 K. Given the specific heat of the metal is c cal/K, find the change in entropy (in cal/K) of the system. Take In 2 = 0.70, In 3 = 1.10, In 4 =1.40, In 5 = 1.61. (A)+2.0 mc(B) +0.6mc(C)-1.0 mc(D) +0.3 mc(E) -0.21 mc

18. A 5.23-g pebble is dropped from a 300-m building. If it reaches a terminal velocity of 40 m/s, and the rest of the energy is converted to heating the coin, what is the change in temperature (in °C) of the coin? (The specific heat of pebble is 400 J/kg.°C Take g = 10 m/s2. )(A)8.5 (B) 2.8 (C) 5.5 (D)21 (E)0.5