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AP Physics 1

AP Physics 1 Unit 2 Forces: Conceptual MCQ (Set A)

Shared by ashtont · Oct 24, 2026 · 0 plays

15 hard conceptual questions for the Unit 2 forces test: third-law pairs, free-body diagrams, apparent weight, static friction, Atwood tension, springs and center of mass. Every choice has an explanation.

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15 questions across 15 sections. After every answer you’ll see why each choice is right or wrong, not just the one you picked.

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Sections (none selected means all)

Sample questions

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

A large truck pushes a small car whose engine is off. They speed up together to the right on a level road. During this time, how does the force exerted by the truck on the car compare to the force exerted by the car on the truck?
  1. A. The truck's force on the car is larger, because the pair is accelerating forward.
  2. B. The truck's force on the car is larger, because the truck has more mass.
  3. C. The forces have equal magnitudes. ✓
  4. D. The car's force on the truck is larger, because the car resists the motion.

Correct answer: C. These forces are a Newton's third-law pair, so they are always equal in magnitude and opposite in direction, whether the objects are accelerating, at rest or colliding. They act on different objects, so they never cancel each other.

A block is launched up a rough incline. It slides upward and slows down. No one is touching it. Which free-body diagram correctly shows the forces on the block while it moves up?
  1. A. Three forces: F_g straight down, F_N perpendicular to the incline surface, and kinetic friction pointing down the slope. ✓
  2. B. Four forces: F_g straight down, F_N perpendicular to the surface, kinetic friction down the slope, and a "force of motion" pointing up the slope.
  3. C. Three forces: F_g straight down, F_N perpendicular to the surface, and kinetic friction pointing up the slope.
  4. D. Three forces: F_g straight down, F_N pointing straight up (vertical), and kinetic friction pointing down the slope.

Correct answer: A. Only Earth (F_g) and the surface (F_N and friction) touch or pull on the block. It moves up the slope, so kinetic friction opposes that motion and points down the slope.

A student stands on a scale in an elevator that is moving DOWNWARD and SLOWING DOWN. How does the scale reading compare to the student's weight mg?
  1. A. Less than mg, because the elevator is moving downward.
  2. B. Equal to mg, because the student's mass hasn't changed.
  3. C. Less than mg, because the elevator is slowing down.
  4. D. Greater than mg, because the acceleration is upward. ✓

Correct answer: D. Moving down while slowing down means the acceleration points up. Then F_N − mg = ma with a > 0, so F_N > mg, and the scale reads the normal force.

A rope pulls a box with tension F_T at 30° above horizontal. The box moves at CONSTANT VELOCITY across a rough floor. Which of the following is true?
  1. A. The normal force equals mg, and friction equals F_T.
  2. B. Friction equals F_T cos 30°, and the normal force is less than mg. ✓
  3. C. F_T cos 30° is greater than friction, because the box is moving forward.
  4. D. Friction equals F_T cos 30°, and the normal force is greater than mg.

Correct answer: B. Constant velocity means ΣF = 0 on both axes. Horizontally, f = F_T cos 30°. Vertically, F_N + F_T sin 30° = mg, so F_N = mg − F_T sin 30°, which is less than mg.

A block of mass M slides on a frictionless horizontal table. A light string runs from M over an ideal pulley at the table's edge to a hanging block of mass m. Both blocks accelerate. — How does the tension F_T compare to the weight of the hanging block, mg?
  1. A. F_T < mg ✓
  2. B. F_T = mg
  3. C. F_T > mg
  4. D. F_T = Mg

Correct answer: A. The hanging block accelerates downward, so the net force on it points down: mg − F_T = ma > 0, which means F_T < mg.