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AP Physics 1

AP Physics 1 Unit 2 Forces: Problem-Solving MCQ (Set B)

Shared by Ashton · Oct 25, 2026 · 0 plays

16 calculation questions for the Unit 2 forces test: F = ma from graphs, elevators, friction, modified Atwood, angled pulls, inclines, springs, center of mass and connected objects. Each wrong choice explains the mistake behind it. Use g = 9.8 m/s².

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16 questions across 16 sections. After every answer you’ll see why each choice is right or wrong, not just the one you picked.

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Sample questions

Open a question to see the answer choices and the correct answer.

A student pushes a 5.0 kg box horizontally across a floor. Friction on the box is 8.0 N. What push makes the box accelerate at 2.4 m/s²?
  1. A. 4.0 N
  2. B. 12 N
  3. C. 20 N ✓
  4. D. 32 N

Correct answer: C. F_push − f = ma, so F_push = 5.0(2.4) + 8.0 = 12 + 8 = 20 N.

Velocity–time graph of a 1200 kg car: v rises in a straight line from 0 at t = 0 to 24 m/s at t = 8 s, then stays at 24 m/s until t = 10 s. — During the first 8 s, air resistance on the car is 900 N. What forward force does the road exert on the car during that time? (g = 9.8 m/s²)
  1. A. 2700 N
  2. B. 3600 N
  3. C. 900 N
  4. D. 4500 N ✓

Correct answer: D. A = slope = 24/8 = 3 m/s². F − F_drag = ma, so F = 1200(3) + 900 = 4500 N.

A 60 kg student stands on a scale in an elevator that accelerates upward at 2.0 m/s². What does the scale read? (g = 9.8 m/s²)
  1. A. 468 N
  2. B. 588 N
  3. C. 708 N ✓
  4. D. 720 N

Correct answer: C. Take up as +. F_N − mg = ma, so F_N = 60(9.8 + 2.0) = 708 N.

A 15 kg crate is pulled horizontally with 80 N across a floor with μₖ = 0.30. What is its acceleration? (g = 9.8 m/s²)
  1. A. 2.39 m/s² ✓
  2. B. 5.03 m/s²
  3. C. 5.33 m/s²
  4. D. 8.27 m/s²

Correct answer: A. F = μₖmg = 0.30(15)(9.8) = 44.1 N, so a = (80 − 44.1)/15 = 2.39 m/s².

A horizontal 60 N force accelerates an 8.0 kg block across a level surface at 4.5 m/s². What is the coefficient of kinetic friction? (g = 9.8 m/s²)
  1. A. 0.40
  2. B. 0.31 ✓
  3. C. 0.46
  4. D. 0.77

Correct answer: B. 60 − f = 8.0(4.5) = 36, so f = 24 N. Then μₖ = f/F_N = 24/(8.0 × 9.8) = 0.31.