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AP Physics 2 · 45 min

Physics 2 mixed model check

A cross-unit check for the AP Physics 2 habit that matters most: choosing the right model before calculating.

rule 1

Write the unit or model beside each question before solving.

rule 2

For fluids, decide whether the problem is pressure-depth, buoyancy, continuity, or streamline energy.

rule 3

For E&M, decide whether the quantity is scalar, vector, or circuit-state dependent.

rule 4

For magnetism, handle q(v × B) before any induction rule.

rule 5

For waves and modern physics, name whether the problem is ray, wave, interference, or photon based.

P2-1 · AP Physics 23 pts

Question 1

Field and potential midpoint

Conceptual translation3 points

At the midpoint between equal charges +q and -q, state whether electric potential and electric field are zero or nonzero. Justify both.

Hint

Potential adds as a scalar; field adds as a vector.

Worked solution

The potential is zero because the scalar contributions cancel. The electric field is nonzero because both field vectors point from the positive charge toward the negative charge.

Trap tested: Using the same cancellation logic for field and potential.

Rubric

  • 1 pt for V = 0 with scalar reasoning.
  • 1 pt for E nonzero with vector direction reasoning.
  • 1 pt for explicitly distinguishing scalar and vector addition.
Electric field is not electric potential
P2-2 · AP Physics 24 pts

Question 2

RC initial and final current

Quantitative reasoning4 points

A 9.0 V battery, 3.0 kΩ resistor, and initially uncharged capacitor are connected in series. Find the current immediately after closing the switch and after a very long time.

Hint

At t = 0 the uncharged capacitor has zero voltage; long after, it acts as an open circuit.

Worked solution

Initially, I₀ = V/R = 9.0 V / 3000 Ω = 3.0 mA. After a very long time, the capacitor is fully charged and steady current is 0 A.

Trap tested: Using one capacitor behavior for both time limits.

Rubric

  • 2 pts for initial current V/R.
  • 1 pt for long-time current of zero.
  • 1 pt for explaining capacitor state in both limits.
Capacitors change role over timeCurrent is not used up
P2-3 · AP Physics 23 pts

Question 3

Isochoric first law

Quantitative reasoning3 points

An ideal gas absorbs 120 J of heat while held at constant volume. Using W as work done by the gas, find W and ΔU.

Hint

Constant volume means no boundary displacement.

Worked solution

W = 0 because the volume does not change. With ΔU = Q - W, ΔU = 120 J.

Trap tested: Assuming heat input automatically means nonzero work.

Rubric

  • 1 pt for W = 0.
  • 1 pt for correct first-law substitution.
  • 1 pt for ΔU = 120 J with sign.
Heat, temperature, and internal energy are different
P2-4 · AP Physics 23 pts

Question 4

Lenz's law direction

Conceptual translation3 points

A loop is in a magnetic field into the page. The field strength is increasing. What direction is the induced magnetic field through the loop, and what current direction produces it?

Hint

The induced field opposes the increase in into-page flux.

Worked solution

The induced field points out of the page. By the right-hand rule, an out-of-page field through the loop is produced by counterclockwise current.

Trap tested: Opposing the field in some cases but forgetting to state the change in flux.

Rubric

  • 1 pt for identifying increasing into-page flux.
  • 1 pt for induced field out of the page.
  • 1 pt for counterclockwise current.
Induced current opposes flux change, not flux
P2-5 · AP Physics 22 pts

Question 5

Refraction frequency

Conceptual translation2 points

Light goes from air into glass. Speed decreases. What happens to frequency and wavelength?

Hint

The source fixes the frequency across the boundary.

Worked solution

Frequency stays the same. Since v = fλ and speed decreases, wavelength decreases.

Trap tested: Changing frequency because speed changed.

Rubric

  • 1 pt for frequency unchanged.
  • 1 pt for wavelength decreases.
Waves, optics, and photons depend on the model you choose
P2-6 · AP Physics 23 pts

Question 6

Photoelectric intensity

Paragraph argument3 points

Light below the threshold frequency shines on a metal. A student doubles the intensity and claims electrons will be emitted. Write a short rebuttal.

Hint

Intensity changes photon rate; frequency sets energy per photon.

Worked solution

The claim is incorrect. Each photon has energy hf, and because f is below threshold, each photon has insufficient energy to eject an electron. Doubling intensity increases the number of low-energy photons per second, not the energy of each photon.

Trap tested: Using classical total energy instead of photon energy per interaction.

Rubric

  • 1 pt for naming threshold frequency or work function.
  • 1 pt for saying energy per photon depends on frequency.
  • 1 pt for explaining what intensity changes.
Waves, optics, and photons depend on the model you choose
P2-7 · AP Physics 23 pts

Question 7

Parallel branch source current

Quantitative reasoning3 points

A 12 Ω resistor is connected to a 6.0 V ideal battery. A second 12 Ω resistor is added in parallel. What happens to total battery current?

Hint

Parallel equivalent resistance gets smaller.

Worked solution

With one resistor, I = 6.0/12 = 0.50 A. With two identical parallel resistors, R_eq = 6.0 Ω, so I_total = 6.0/6.0 = 1.0 A. The total battery current doubles.

Trap tested: Keeping total current fixed and only splitting it between branches.

Rubric

  • 1 pt for initial current.
  • 1 pt for R_eq = 6.0 Ω or equivalent reasoning.
  • 1 pt for total current doubling to 1.0 A.
Current is not used upCapacitors change role over time
P2-8 · AP Physics 23 pts

Question 8

Floating fraction

Quantitative reasoning3 points

A block floats in water with 60 percent of its volume submerged. What is the block's average density in terms of water density?

Hint

For floating equilibrium, buoyant force equals weight.

Worked solution

At equilibrium, rho_water V_sub g = rho_block V_total g. Since V_sub/V_total = 0.60, rho_block = 0.60 rho_water.

Trap tested: Using the full object volume as displaced volume even though only the submerged part displaces water.

Rubric

  • 1 pt for setting buoyant force equal to weight.
  • 1 pt for using submerged volume, not total volume, in the displaced-fluid term.
  • 1 pt for rho_block = 0.60 rho_water.
Pressure, buoyancy, and flow are different fluid models
P2-9 · AP Physics 23 pts

Question 9

Magnetic radius scaling

Quantitative reasoning3 points

A charged particle enters a uniform magnetic field perpendicular to its velocity and follows a circular path. Derive how the radius depends on speed, mass, charge, and field strength. Then state what happens to the radius if B is doubled.

Hint

Magnetic force supplies the centripetal force.

Worked solution

|q|vB = mv²/r, so r = mv/(|q|B). Doubling B halves the radius if m, v, and |q| stay fixed.

Trap tested: Treating qvB as a force along the field instead of the inward force that bends the path.

Rubric

  • 1 pt for setting magnetic force equal to centripetal force.
  • 1 pt for r = mv/(|q|B).
  • 1 pt for radius halving when B doubles.
Magnetic force is perpendicular to velocity and field

score What it means

Use the score to choose the next repair.

23-27 pts

AP2 model choices are stable

Move into timed mixed AP Physics 2 free-response practice.

15-22 pts

Good but unit-switching is uneven

Redo the lessons connected to the two lowest-scoring questions.

0-14 pts

Repair model choice first

Work untimed through fluids, fields, RC states, thermo signs, magnetism, and wave/photon model choice.

after Turn the mock into data

If you missed a question, do not just reread the solution. Open the linked lesson, redo one drill, then come back to the mock.

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