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Physics Principles Flashcards

7 cards from real OAT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Physics Principles flashcards as text

  1. A charge of +2 μC is placed 3 cm from a charge of −2 μC. What is the magnitude of the electrostatic force between them? (k = 9 × 10⁹ N·m²/C²)

    Answer: 40 N

    F = kq₁q₂/r² = (9×10⁹)(2×10⁻⁶)(2×10⁻⁶)/(0.03)² = 36×10⁻³/9×10⁻⁴ = 40 N.

  2. Which of the following best explains why a spinning ice skater speeds up when they pull their arms in?

    Answer: Conservation of angular momentum requires angular velocity to increase as moment of inertia decreases

    With no external torque, L = Iω is constant; pulling arms in decreases I, so ω must increase.

  3. A sound source produces a 400 Hz tone. An observer moves toward the source at 34 m/s. If the speed of sound is 340 m/s, what frequency does the observer hear?

    Answer: 440 Hz

    f' = f(v + v_observer)/v = 400 × (340 + 34)/340 = 400 × 374/340 ≈ 440 Hz.

  4. In a transformer, the primary coil has 100 turns and the secondary has 500 turns. If the primary voltage is 120 V, what is the secondary voltage?

    Answer: 600 V

    V_s/V_p = N_s/N_p → V_s = 120 × (500/100) = 600 V.

  5. A fluid flows through a pipe that narrows from a cross-sectional area of 0.04 m² to 0.01 m². If the initial flow speed is 2 m/s, what is the speed in the narrower section?

    Answer: 8 m/s

    By the continuity equation: A₁v₁ = A₂v₂ → v₂ = (0.04 × 2)/0.01 = 8 m/s.

  6. A radioactive isotope has a half-life of 10 days. What fraction of the original sample remains after 30 days?

    Answer: 1/8

    30 days = 3 half-lives; fraction remaining = (1/2)³ = 1/8.

  7. Which thermodynamic process occurs at constant pressure?

    Answer: Isobaric

    An isobaric process occurs at constant pressure, so work done by the gas equals PΔV.