所屬科目：研究所、轉學考(插大)◆普通物理學
1. In the figure, a uniform rectangular crate 0.40 m wide and 1.0 m tall rests on a horizontal surface. The crate weighs 1000 N, and its center of gravity is at its geometric center. A horizontal force F is applied at a distance h above the floor. If h = 0.8 m, what minimum value of F is required to make the crate start to tip over? (Static friction is large enough that the crate does not start to slide.)
(A) 500 N(B) 750 N(C) 250 N(D) 625 N(E) 1000 N
2. A record is dropped vertically onto a freely rotating turntable (kinetic energy of the record is negligible). Frictional forces act to bring the record and turntable to a common angular speed. If the rotational inertia of the record is 0.66 times that of the turntable, what percentage of the initial kinetic energy is lost?(A) 40%(B) 34%(C) 56%(D) 66%(E) 19%
3. A 15-g bullet is shot vertically into a 2-kg block. The block lifts upward 8.0 mm. The bullet penetrates the block and comes to rest in it in a time interval of 0.0010 s. Assume the force on the bullet is constant during penetration and that air resistance is negligible. The kinetic energy of the bullet lost in the block is closest to
(A) 14 J(B) 21 J(C) 0.16 J(D) 0.0012 J(E) 10 J
4. A satellite is in circular orbit at an altitude of 2300 km above the surface of a nonrotating asteroid with an orbital speed of 5.9 km/s. The minimum speed needed to escape from the surface of the asteroid is 14.6 km/s. The mass of the asteroid is closest to(A) 3.0 × 10²⁴ kg(B) 9.0 × 10²³ kg(C) 1.0 × 10²⁴ kg(D) 2.0 × 10²⁴ kg(E) 4.0 × 10²⁴ kg
5. Is it possible for a system to have negative potential energy?(A) No, because this would have no physical meaning.(B) No, because the kinetic energy of a system must equal its potential energy.(C) Yes, as long as the kinetic energy is positive.(D) Yes, as long as the total energy is positive.(E) Yes, since the choice of the zero of potential energy is arbitrary.
6. An experimental rocket sits on its launching pad on earth pointing vertically upwards. Its total mass is 7×10⁶kg, of which 6.5 × 10⁶ kg is fuel. Its engines shoot exhaust downward at a rate of 2000 kg/s with a speed of 3000 m/s relative to the rocket. Calculate the approximate delay between ignition and lift off.(A) It never lifts off.(B) 53 minutes(C) 27 minutes(D) 1 minutes(E) No delay
7. A 2.0 kg block on a frictionless table is connected to two ideal massless springs with spring constants k₁ and k₂ whose opposite ends are fixed to walls, as shown in the figure. What is angular frequency of the oscillation if k₁ = 7.5 N/m and k₂ = 5.0 N/m?
(A) 2.5 rad/s(B) 3.5 rad/s(C) 0.40 rad/s(D) 0.56 rad/s(E) 1.2 rad/s
8. Upon being struck by 240-nm photons, a metal ejects electrons with a maximum kinetic energy of 1.45 eV. What is the work function of this metal?(A) 5.18 eV(B) 4.92 eV(C) 4.33 eV(D) 3.73 eV(E) 3.13 eV
9. In the figure, an open tank contains a layer of oil floating on top of a layer of water (of density 1000 kg/m³) that is 3.0 m thick. What must be the thickness of the oil layer if the gauge pressure at the bottom of the tank is to be 5.0 × 10⁴ Pa? The density of the oil is 510 kg/m³.
(A) 9.2 m(B) 8.2 m(C) 4.1 m(D) 2.0 m(E) 1.2 m
10. Two metal rods, one silver and the other copper, are both attached to a steam chamber as shown in the figure, with a temperature of 100°C, at one end, and an ice water bath, with a temperature of 0°C, at the other. The rods are 5.0 cm long and have a square cross-section, 2.0 cm on a side. When steady state has been reached, how much heat flows through the two rods in 1.0 min? The thermal conductivity of silver is 417 W/(m·K), and that of copper is 395 W/(m·K). No heat is exchanged between the rods and the surroundings, except at their ends.
(A) 20 kJ(B) 11 kJ(C) 49 kJ(D) 47 kJ(E) 39 kJ
11. The figure shows a 50-kg frictionless cylindrical piston that floats on 0.68 mol of compressed air at 30°C. How far does the piston move if the temperature is increased to 300°C?
(A) 1300 cm(B) 250 cm(C) 130 cm(D) 120 cm(E) 60 cm
12. A solid nonconducting sphere of radius R carries a charge Q distributed uniformly throughout its volume. At a certain distance r₁ (r₁ ＜ R) from the center of the sphere, the electric field has magnitude E. If the same charge Q were distributed uniformly throughout a sphere of radius 3R, the magnitude of the electric field at the same distance r₁ from the center would be equal to(A) E/9(B) E/3(C) 3E(D) 9E(E) E
13. Each plate of a parallel-plate air-filled capacitor has an area of 0.0020 m², and the separation of the plates is 0.020mm. An electric field of 3.9 × 10⁶ V/m is present between the plates. What is the surface charge density on the plates?(A) 17 μC/m²(B) 35 μC/m²(C) 52 μC/m²(D) 73 μC/m²(E) 87 μC/m²
14. A uniform magnetic field of magnitude 0.80 T in the negative z-direction is present in a region of space, as shown in the figure. A uniform electric field is also present. An electron that is projected with an initial velocity v₀ = 9.1 × 10⁴ m/s in the positive x-direction passes through the region without deflection. What is the electric field vector? (êx and êy are unit vectors in x- and y-directions, respectively)
(A) +110 kV/m êx(B) -110 kV/m êy(C) +73 kV/m êx(D) -73 kV/m êy(E) None of the above.
15. When an LRC series circuit is at resonance, which one of the following statements about that circuit is accurate?(A) The impedance has its maximum value.(B) The reactance of the inductor is zero.(C) The reactance of the capacitor is zero.(D) The reactance due to the inductor and capacitor has its maximum value.(E) The current amplitude is a maximum.
16. A very small source of light that radiates uniformly in all directions produces an electric field amplitude of 2.96 V/m at a point 33.0 m from the source. What is the average power output from the source?(A) 102 W(B) 159 W(C) 256 W(D) 80 W(E) 318 W
17. A capacitor is charging in a simple RC circuit with a dc battery. Which one of the following statements about this capacitor is accurate?(A) There is a magnetic field between the capacitor plates because charge travels between the plates by jumping from one plate to the other.(B) There is no magnetic field between the capacitor plates because no charge travels between the plates.(C) There is a magnetic field between the capacitor plates, even though no charge travels between them, because the electric flux between the plates is changing.(D) There is a magnetic field between the capacitor plates, even though no charge travels between them, because the magnetic flux between the plates is changing.(E) The magnetic field between the capacitor plates is increasing with time because the charge on the plates is increasing.
18. When light goes from one material into another material having a higher index of refraction,(A) its speed, wavelength, and frequency all decrease.(B) its speed decreases but its frequency and wavelength stay the same.(C) its speed decreases but its wavelength and frequency both increase.(D) its speed increases, its wavelength decreases, and its frequency stays the same.(E) its speed and wavelength decrease, but its frequency stays the same.
19. A energetic particle is moving at 0.866c in a 200 m-long linear particle accelerator. How long does the particle accelerator appear to the particle?(A) 100 m(B) 200 m(C) 400 m(D) 173 m(E) 231 m
20. An electron is in an infinite square well (a box) that is L = 2.0 nm wide. The electron makes a transition from the n = 8 to the n = 7 state, what is the wavelength of the emitted photon? (hint: the energy levels for an infinite square well potential is )(A) 1100 nm(B) 1000 nm(C) 880 nm(D) 750 nm(E) 610 nm
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