MCAT Physics 2 — Questions and Answers
Question 1: A 2 kg block slides down a frictionless incline of 30°. What is the block's acceleration along the incline?
- 4.9 m/s² (Correct answer)
- 9.8 m/s²
- 8.5 m/s²
- 2.45 m/s²
Correct 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.
Question 2: A spring with spring constant k = 200 N/m is compressed by 0.1 m. How much potential energy is stored?
- 2 J
- 1 J (Correct answer)
- 20 J
- 0.1 J
Correct answer: 1 J
Elastic potential energy = ½kx² = ½ × 200 × (0.1)² = 1 J.
Question 3: Which of the following best describes the Doppler effect when a sound source moves toward a stationary observer?
- Observed frequency is lower than emitted frequency
- Observed frequency equals emitted frequency
- Observed frequency is higher than emitted frequency (Correct answer)
- Wavelength increases as source approaches
Correct 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.
Question 4: 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?
- 0.5 m/s
- 4 m/s
- 8 m/s (Correct answer)
- 2 m/s
Correct answer: 8 m/s
By continuity, A₁v₁ = A₂v₂, so v₂ = (0.04 × 2) / 0.01 = 8 m/s.
Question 5: 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?
- Away from the negative charge
- Toward the negative charge (Correct answer)
- Perpendicular to the line joining the charges
- There is no force
Correct answer: Toward the negative charge
Opposite charges attract, so the positive charge experiences a force directed toward the negative charge.
Question 6: 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?
- 4.47 m/s (Correct answer)
- 20 m/s
- 5 m/s
- 2.24 m/s
Correct answer: 4.47 m/s
Centripetal acceleration a = v²/r, so v = √(ar) = √(10 × 2) = √20 ≈ 4.47 m/s.
Question 7: 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?
- 1 A
- 2 A (Correct answer)
- 4 A
- 5 A
Correct answer: 2 A
Total resistance = 4 + 6 = 10 Ω; current I = V/R = 20/10 = 2 A.
MCAT Physics 2
A 2 kg block slides down a frictionless incline of 30°.
What is the block's acceleration along the incline?