【GR0877】 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 

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1. A ball is thrown out of the passenger window of a car moving to the right (ignore air resistance). If the ball is thrown out perpendicular to the velocity of the car, which of the following best depicts the path the ball takes, as viewed from above?

 

 

⑴ answer: B

⑵ The ball follows a uniform motion of straight line.

 

2. An object is thrown horizontally from the open window of a building. If the initial speed of the object is 20 m/s and it hits the ground 2.0 s later, from what height was it thrown? (Neglect air resistance and assume the ground is level.)

 

 

⑴ answer: D

⑵ h = 1/2 × g × t² = 1/2 × 9.8 × 2² = 19.6 m

 

 

3. A resistor in a circuit dissipates energy at a rate of 1 W. If the voltage across the resistor is doubled, what will be the new rate of energy dissipation?

 

 

⑴ answer: E

⑵ P = V² / R 

 

 

4. An infinitely long, straight wire carrying current I₁ passes through the center of a circular loop of wire carrying current I₂, as shown below. The long wire is perpendicular to the plane of the loop. Which of the following describes the magnetic force on the loop?

 

 

⑴ answer: E

⑵ Lorentz force : The magnetic field made by I₁ is parallel to I₂, resulting in no force on the loop. 

 

 

5. De Broglie hypothesized that the linear momentum and wavelength of a free massive particle are related by which of the following constants?

 

 

⑴ answer: A

⑵ p = mv = h / λ

 

 

6. An atom has filled n = 1 and n = 2 levels. How many electrons doest the atom have?

 

 

⑴ answer: E

⑵ an atom of Ne 

 

 

7. The root-mean-square speed of molecules of mass m in an ideal gas at temperature T is 

 

 

⑴ answer: C

⑵ root mean square velocity

 

 

 

8. The energy from electromagnetic waves in equilibrium in a cavity is ued to melt ice. If the Kelvin temperature of the cavity is increased by a factor of two, the mass of ice that can be melted in a fixed amount of time is increased by a factor of 

 

 

⑴ answer: D

⑵ Stefan-Boltzmann law 

 

 

 

9. The figure below represents the orbit of a planet around a star, S, and the marks divide the orbit into 14 equal time intervals, t = T / 14, where T is the orbital period. If the only force acting on the planet is Newtonian gravitation, then true statements about the situation include which of the following?

 

 

⑴ answer: E

⑵ Ⅰ : Kepler's second law 

⑶ Ⅱ : Kepler's first law 

⑷ Ⅲ : Kepler's third law 

 

 

10. A massless spring with force constant k launches a ball of mass m. In order for the ball to reach a speed v, by what displacement s should be the spring be compressed?

 

 

⑴ answer: B 

 

 

 

11. A quantum mechanical harmonic oscillator has an angular frequency ω. The Schrödinger equation predicts that the ground state energy of the oscillator will be 

 

 

⑴ answer: C

 

 

12. In the Bohr model of the hydrogen atom, the linear momentum of the electron at radius r_n is given by which of the following? (n is the principal quantum number.)

 

 

⑴ answer: C

⑵ Eq 1. nλ = 2πr_n

⑶ Eq 2. de Broglie equation : pλ = h

⑷ ∴ p = h / λ = nℏ / r_n   

 

 

13. The figure below represents a log-log plot of variable y versus variable x. The origin represents the point x = 1 and y = 1. Which of the following gives the approximate functional relationship between y and x?

 

 

⑴ answer: A

⑵ Δ log y / Δ log x = 0.5 

 

 

14. Two experimental techniques determine the mass of an object to be 11 ± 1 kg and 10 ± 2 kg. These two measurements can be combined to give a weighted average. The uncertainty of the weighted average is equal to which of the following?

 

 

⑴ answer: B
⑵ σ₁² = 1, σ₂² = 4

⑶ w₁ = 1 / σ₁² = 1, w₂ = 1 / σ₂² = 0.25

⑷ 1 / ∑ w_i = 0.8

⑸ ∴ σ_average = √ 0.8

 

 

15. If the five lenses shown below are made of the same material, which lens has the shortest positive focal length?

 

 

⑴ answer: E

⑵ lens maker's formula

 

 

 

16. Unpolarized light is incident on a pair of ideal linear polarizers whose transmission axes make an angle of 45° with each other. The transmitted light intensity through both polarizers is what percentage of the incident intensity?

 

 

⑴ answer: D

⑵ Malus law

 

 

 

17. A very long, thin, straight wire carries a uniform charge density of λ per unit length. Which of the following gives the magnitude of the electric field at a radial distance r from the wire?

 

 

⑴ answer: A

⑵ Gauss law 

 

 

 

18. The bar magnet shown in the figure below is moved completely through the loop. Which of the following is a true statement about the direction of the current flow between the two points a and b in the circuit?

 

 

⑴ answer: E

⑵ Lenz's law 

 

 

 

19. The surface of the Sun has a temperature close to 6,000 K and it emits a blackbody (Planck) spectrum that reaches a maximum near 500 nm. For a body with a surface temperature close to 300 K, at what wavelength would the thermal spectrum reach a maximum?

 

 

⑴ answer: A

⑵ Wien's displacement law : 6000 × 500 nm = 300 × x ⇔ x = 10 μm 

 

 

20. At the present time, the temperature of the universe (i.e., the microwave radiation background) is about 3 K. When the temperature was 12 K, typical objects in the universe, such as galaxies, were

 

 

⑴ answer: A

⑵ Wien's displacement law

⑶ The wavelength decreases by about four times, and the distance is about that.

 

입력: 2023.10.06 21:15