AP Physics Physics: Classical Mechanics & Kinematics 2 — Questions and Answers
Question 1: A projectile is launched at 30° above the horizontal with an initial speed of 20 m/s. What is the maximum height reached? (g = 10 m/s²)
- 2.5 m
- 5 m (Correct answer)
- 10 m
- 20 m
Correct answer: 5 m
The vertical component is 20sin(30°) = 10 m/s; max height = v²/(2g) = 100/20 = 5 m.
Question 2: A 5 kg block slides down a frictionless incline of angle 37°. What is the block's acceleration? (g = 10 m/s², sin37° ≈ 0.6)
- 4 m/s²
- 6 m/s² (Correct answer)
- 8 m/s²
- 10 m/s²
Correct answer: 6 m/s²
On a frictionless incline, a = g·sinθ = 10 × 0.6 = 6 m/s².
Question 3: Two objects with masses 2 kg and 4 kg experience the same net force. What is the ratio of their accelerations (a₂ kg / a₄ kg)?
- 1:2
- 2:1 (Correct answer)
- 1:4
- 4:1
Correct answer: 2:1
From F = ma, acceleration is inversely proportional to mass, so a₂/a₄ = m₄/m₂ = 4/2 = 2:1.
Question 4: A car traveling at 20 m/s decelerates uniformly and stops in 4 seconds. What distance does it travel while stopping?
- 20 m
- 40 m (Correct answer)
- 60 m
- 80 m
Correct answer: 40 m
Using d = (v₀ + v)/2 × t = (20 + 0)/2 × 4 = 40 m.
Question 5: Which of the following correctly describes the velocity of an object in uniform circular motion?
- Constant in magnitude and direction
- Changing in magnitude, constant in direction
- Constant in magnitude, changing in direction (Correct answer)
- Changing in both magnitude and direction
Correct answer: Constant in magnitude, changing in direction
In uniform circular motion, speed (magnitude of velocity) is constant but direction continuously changes.
Question 6: A 10 kg box is pushed across a floor with a coefficient of kinetic friction μₖ = 0.3. What friction force acts on the box? (g = 10 m/s²)
- 3 N
- 10 N
- 30 N (Correct answer)
- 100 N
Correct answer: 30 N
f_k = μₖ × N = μₖ × mg = 0.3 × 10 × 10 = 30 N.
Question 7: An object is thrown vertically upward. At its peak, which statement is true?
- Velocity is zero and acceleration is zero
- Velocity is zero and acceleration is g downward (Correct answer)
- Velocity is maximum and acceleration is zero
- Both velocity and acceleration are directed downward
Correct answer: Velocity is zero and acceleration is g downward
At the peak, velocity momentarily equals zero, but gravitational acceleration (g ≈ 9.8 m/s² downward) acts throughout the flight.
AP Physics Physics: Classical Mechanics & Kinematics 2
A projectile is launched at 30° above the horizontal with an initial speed of 20 m/s.
What is the maximum height reached? (g = 10 m/s²)