Physics Flashcards

A 2 kg block slides down a frictionless incline of 30°. What is the block's acceleration along the incline?

Answer: 4.9 m/s²

Acceleration along a frictionless incline is g·sin(θ) = 9.8 × sin(30°) = 9.8 × 0.5 = 4.9 m/s².

A spring with spring constant k = 200 N/m is compressed by 0.1 m. How much potential energy is stored?

Answer: 1 J

Elastic potential energy = ½kx² = ½ × 200 × (0.1)² = 1 J.

Which of the following best describes the Doppler effect when a sound source moves toward a stationary observer?

Answer: Observed frequency is higher than emitted frequency

When a source moves toward an observer, sound wavefronts bunch together, shortening wavelength and increasing observed frequency.

A fluid flows through a pipe that narrows from a cross-sectional area of 0.04 m² to 0.01 m². If the fluid velocity in the wide section is 2 m/s, what is the velocity in the narrow section?

Answer: 8 m/s

By continuity, A₁v₁ = A₂v₂, so v₂ = (0.04 × 2) / 0.01 = 8 m/s.

Two point charges of +2 μC and −2 μC are separated by 0.1 m. What is the direction of the electrostatic force on the positive charge?

Answer: Toward the negative charge

Opposite charges attract, so the positive charge experiences a force directed toward the negative charge.

An object moving in uniform circular motion has a centripetal acceleration of 10 m/s² at a radius of 2 m. What is the object's speed?

Answer: 4.47 m/s

Centripetal acceleration a = v²/r, so v = √(ar) = √(10 × 2) = √20 ≈ 4.47 m/s.

In a series circuit, two resistors of 4 Ω and 6 Ω are connected to a 20 V battery. What is the current through the circuit?

Answer: 2 A

Total resistance = 4 + 6 = 10 Ω; current I = V/R = 20/10 = 2 A.