Military Nursing Service (MNS) Entrance Physics Flashcards

24 sample cards from the Physics deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. State the postulates of the kinetic theory of gases.

   Gas consists of a large number of identical molecules in random motion; molecular size is negligible compared to distances; collisions are perfectly elastic; no intermolecular forces except during collisions; time of collision is negligible.

2. Give the kinetic theory expression for gas pressure and the relation for mean KE.

   P = (1/3)(mN/V)v_rms^2 = (1/3)ρv_rms^2. Average translational KE per molecule = (3/2)kT, where k is Boltzmann's constant.

3. State the law of equipartition of energy and define degrees of freedom.

   Energy is shared equally among all available degrees of freedom, each contributing ½kT per molecule. Degrees of freedom = number of independent ways a molecule can store energy (e.g. monatomic = 3, diatomic = 5).

4. State the first law of thermodynamics.

   Heat supplied to a system equals the increase in internal energy plus the work done by the system: ΔQ = ΔU + ΔW. It is a statement of conservation of energy.

5. State the second law of thermodynamics (Kelvin-Planck and Clausius statements).

   Kelvin-Planck: no engine can convert all heat from a single reservoir entirely into work. Clausius: heat cannot flow spontaneously from a colder to a hotter body without external work.

6. Give the efficiency of a Carnot engine and coefficient of performance of a refrigerator.

   Carnot efficiency η = 1 - T_cold/T_hot (temperatures in kelvin). Refrigerator COP = T_cold/(T_hot - T_cold).

7. Compare isothermal and adiabatic processes.

   Isothermal: temperature constant, ΔU = 0, PV = constant, slow process. Adiabatic: no heat exchange (ΔQ = 0), PV^γ = constant, fast process; in adiabatic expansion temperature falls.

8. Define simple harmonic motion and give its defining equation.

   SHM is motion in which the restoring force (and acceleration) is directly proportional to displacement and directed toward the mean position: a = -ω^2x.

9. Give the time period of a simple pendulum and of a mass-spring system.

   Simple pendulum: T = 2π√(L/g). Spring-mass: T = 2π√(m/k).

10. In SHM, where are velocity and acceleration maximum and minimum?

    Velocity is maximum at the mean position (v_max = Aω) and zero at the extremes. Acceleration is maximum at the extremes (a_max = Aω^2) and zero at the mean position.

11. Differentiate transverse and longitudinal waves with examples.

    Transverse: particle vibration perpendicular to wave direction (e.g. light, waves on a string). Longitudinal: particle vibration parallel to wave direction (e.g. sound waves).

12. Give the wave relation between speed, frequency, and wavelength.

    v = fλ (wave speed = frequency × wavelength). Also v = λ/T.

13. What is the principle of superposition, and what are beats?

    When two or more waves overlap, the resultant displacement is the algebraic sum of the individual displacements. Beats are periodic variations in loudness from two waves of slightly different frequencies; beat frequency = |f1 - f2|.

14. Give the speed of sound in a gas (Laplace correction) and how it varies with temperature.

    Laplace: v = √(γP/ρ). In air, speed increases with temperature, roughly v ∝ √T; it increases about 0.61 m/s per °C rise.

15. State the Doppler effect for sound.

    The apparent change in frequency due to relative motion between source and observer. f' = f (v ± v_o)/(v ∓ v_s), where v is sound speed, v_o observer speed, v_s source speed (signs chosen so approach raises pitch).

16. State Coulomb's law and give the permittivity of free space.

    F = (1/4πε0) q1q2/r^2; force is along the line joining the charges. ε0 = 8.85×10^-12 C^2 N^-1 m^-2, and 1/4πε0 ≈ 9×10^9 N m^2 C^-2.

17. Define electric field and electric potential.

    Electric field E = F/q (force per unit positive charge, N/C or V/m). Electric potential V = W/q (work done per unit charge in bringing it from infinity, unit volt).

18. State Gauss's law.

    The total electric flux through a closed surface equals 1/ε0 times the net charge enclosed: Φ = ∮E·dA = q_enclosed/ε0.

19. Give the formula for capacitance of a parallel-plate capacitor and energy stored.

    C = ε0A/d (with dielectric, C = Kε0A/d). Energy stored U = ½CV^2 = ½QV = Q^2/2C.

20. State Ohm's law and give the formula for resistance in terms of resistivity.

    V = IR (current is proportional to potential difference at constant temperature). R = ρL/A, where ρ is resistivity, L length, A cross-sectional area.

21. Give the rules for resistors and capacitors in series and parallel.

    Resistors series: R = R1+R2+...; parallel: 1/R = 1/R1+1/R2+... Capacitors series: 1/C = 1/C1+1/C2+...; parallel: C = C1+C2+...

22. State Kirchhoff's two laws.

    Junction (current) law: the sum of currents entering a junction equals the sum leaving (conservation of charge). Loop (voltage) law: the algebraic sum of potential differences around any closed loop is zero (conservation of energy).

23. State the right-hand rule for magnetic force and give the force on a current-carrying conductor.

    Force F = IL × B, magnitude F = BIL sinθ. Direction is given by F = qv × B for a charge or the right-hand rule; on a moving charge F = qvB sinθ.

24. State Faraday's laws of electromagnetic induction and Lenz's law.

    Induced EMF = -dΦ/dt (rate of change of magnetic flux). Lenz's law: the induced current opposes the change in flux that produces it, ensuring conservation of energy (the negative sign).

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