【GR8677】 The Solution for GRE Physics Practice Test [01-20]

The Solution for GRE Physics Practice Test [01-20]

 

추천글 : 【GRE】 Solution for GRE Physics Practice Test 

---

 

1. A rock is thrown vertically upward with initial speed v₀. Assume a friction force proportional to -v, where v is the velocity of the rock, and neglect the buoyant force exerted by air. Which of the following is correct?

 

 

⑴ answer: B

⑵ 🄐, 🄑, 🄒 : F = ma = mg - bv ≠ mg

⑶ 🄓, 🄔 : The friction make things lose energy, thus decrease velocity. 

 

2. A satellite orbits the Earth in a circular orbit. An astronaut on board perturbs the orbit slightly by briefly firing a control jet aimed toward the Earth's center. Afterward, which of the following is true of the satellite's path?

 

 

⑴ answer: A

⑵ Kepler's law of elliptical orbits

 

 

3. For blue light, a transparent material has a relative permittivity (dielectric constant) of 2.1 and a relative permeability of 1.0. If the speed of light in a vacuum is c, the phase velocity of blue light in an unbounded medium of this material is

 

 

⑴ answer: D

 

 

 

4. The equation y = A sin 2π (t/T - x/λ), where A, T, and λ are positive constants, represents a wave whose 

 

 

⑴ answer: E

⑵ v = λf = λ / T for all waves

 

 

5. Two small spheres of putty, A and B, of mass M and 3M, respectively, hang from the ceiling on strings of equal length ℓ. Sphere A is drawn aside so that it is raised to a height h₀ as shown below and then released. Sphere A collides with sphere B; they stick together and swing to a maximum height h equal to 

 

 

⑴ answer: A

⑵ velocity of A before collision

 

 

⑶ velocity of A and B after collision

 

 

⑷ final height 

 

 

 

6. A particle is initially at rest at the top of a curved frictionless track. The x- and y-coordinates of the track are related in dimensionless units by y = x² / 4, where the positive y-axis is in the vertical downward direction. As the particle slides down the track, what is its tangential acceleration?

 

 

⑴ answer: D

 

 

 

7. A 2-kilogram box hangs by a massless rope from a ceiling. A force slowly pulls the box horizontally to the side until the horizontal force is 10 newtons. The box is then in equilibrium as shown below. The angle that the rope makes with the vertical is closest to 

 

 

⑴ answer: A

 

 

 

8. A 5-kilogram stone is dropped on a nail and drives the nail 0.025 meter into a piece of wood. If the stone is moving at 10 meters per second when it hits the nail, the average force exerted on the nail by the stone while the nail is going into the wood is most nearly

 

 

⑴ answer: D

 

 

 

9. A wire of diameter 0.02 meter contains 1 × 10²⁸ free electrons per cubic meter. For an electric current of 100 amperes, the drift velocity for free electrons in the wire is most nearly 

 

 

⑴ answer: D

⑵ I = Sev_en 

 

 

 

10. An isolated sphere of radius R contains a uniform volume distribution of positive charge. Which of the curves on the graph below correctly illustrates the dependence of the magnitude of the electric field of the sphere as a function of the distance r from its center?

 

 

⑴ answer: C

 

 

 

11. Which of the following equations is a consequence of the quation ∇ × H = D' + J?

 

 

⑴ answer: A

⑵ ∇ · (D' + J) = ∇ · (∇ × H) = 0

 

 

12. A source of 1-kilohertz sound is moving straight toward you at a speed 0.9 times the speed of sound. The frequency you receive is 

 

 

⑴ answer: E

⑵ Doppler effect

 

 

 

13. Two coherent sources of visible monochromatic light from an interference pattern on a screen. If the relative phase of the sources is varied from 0 to 2π at a frequency of 500 hertz, which of the following best describes the effect, if any, on the interference pattern?

 

 

⑴ answer: E

 

 

14. For an ideal gas, the specific heat at constant pressure C_p is greater than the specific heat at constant volume C_v because the

 

 

⑴ answer: A

⑵ C_p = dq_p / dt = C_v + R = dq_v / dt + R 

 

 

15. A sample of N atoms of helium gas is confined in a 1.0 cubic meter volume. The probability that none of the helium atoms is in a 1.0 × 10^-6 cubic meter volume of the container is

 

 

⑴ answer: C

⑵ The probability of an atom to be located outside the indicated small volume : 1 - 10^-6

⑶ The question is related to the law of independent probility.

 

 

16. Except for mass, the properties of the muon most closely resemble the properties of the 

 

 

⑴ answer: A

⑵ Electron and muon are all leptones.

 

 

17. Suppose that ^A_ZX decays by natural radioactivity in two stages to ^A-4_Z-1Y. The two stages would most likely be which of the following? 

 

 

⑴ answer: A

⑵ β^- emission : n → p + e^-

⑶ α emission : He atom (i.e., p₂n₂) is emitted.

 

 

18. The wave function ψ (x) = A exp {- b²x² / 2}, where A and b are real constants, is a normalized eigenfunction of the Schrödinger equation for a particle of mass M and energy E in a one dimensional potential V(x) such that V(x) = 0 at x = 0. Which of the following is correct?

 

 

⑴ answer: B

⑵ I'm not sure, but the following seems to be relevant.

 

 

 

19. The energy levels of the hydrogen atom are given in terms of the principal quantum number n and a positive constant A by the expression

 

 

⑴ answer: E

⑵ Bohr's atom model

⑶ A is Rydberg constant.

 

 

 

20. A positive kaon (K⁺) has a rest mass of 494 MeV / c², whereas a proton has a rest mass of 938 MeV / c². If a kaon has a total energy that is equal to the proton rest energy, the speed of the kaon is most nearly 

 

 

⑴ answer: E

⑵ Einstein's special theory of relativity

 

 

입력: 2023.07.29 10:11