OAT Physics Principles 5

Question 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)

Accepted Answer

40 N

Answer

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

Question 2

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

Accepted Answer

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

Answer

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

Question 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?

Accepted Answer

440 Hz

Answer

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

Question 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?

Accepted Answer

600 V

Answer

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

Question 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?

Accepted Answer

8 m/s

Answer

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

OAT - Optometry Admission Test Practice Test

OAT - Optometry Admission Test Practice Test

OAT Physics Principles 5