2027 AP Physics C Updates
Since the publication of Barron’s AP Physics C Premium, 8th Edition, the College Board has announced minor updates to the format of the May 2027 exam. These updates affect only the number of multiple-choice questions and the timing for both sections of the exam; they do not change the course content, skills assessed, or topics students are expected to know for the exam.
Barron's AP Physics C Premium, 8th Edition remains a comprehensive resource for AP Physics C exam preparation, which provides thorough content review, extensive AP-style practice, and proven test-taking support.
The updates are as follows:
- Section I now has 42 multiple-choice questions (an increase of 2 questions).
- Students now have 85 minutes to complete the multiple-choice questions in Section I (an increase of 5 minutes).
- Students now have 95 minutes to complete the free-response questions in Section II (a decrease of 5 minutes).
Previous Format | Updated 2027 Format | |
|---|---|---|
Section I: Multiple-Choice | 40 questions 80 minutes | 42 questions 85 minutes |
Section II: Free-Response | 4 questions 100 minutes | 4 questions 95 minutes |
To reflect the updated exam format, below are two additional multiple-choice questions (Questions 41 and 42) for each practice test in the book, along with their respective answer explanations. In addition, both online tests that accompany this book have been revised to reflect the exam format updates.
Diagnostic Test: Mechanics
41. A small mass is placed on a disk which rotates in a horizontal plane at constant angular velocity. The mass remains on the disk at the point where it was placed. The acceleration of the mass is
(A) directed perpendicular to the line joining the mass and the axis of rotation.
(B) independent (in magnitude) of the position of the mass on the disk.
(C) greater the closer the mass is to the axis of rotation.
(D) greater the farther the mass is from the axis of rotation
42.Which of the following statements is true?
(A) The angular momentum of a moving object depends on the choice of origin for computing the angular momentum.
(B) An object moving with constant velocity must have zero angular momentum.
(C) If the torque acting on an object is zero for a given choice of origin, then the angular momentum of the object must also be zero for this origin.
(D) If the torque acting on an object is nonzero, then the magnitude of the angular momentum must change with time.
Answer Explanations
41. (D) The acceleration of the mass is centripetal, i.e., pointing towards the axis of rotation, so choice (A) is incorrect. The magnitude of centripetal acceleration is given by a=v2/r. Thus, choice (D) is correct.
42. (A) Angular momentum is defined by L = r x p so choice (A) is correct. Choice (B) is not correct: P can be a constant vector but the cross product with r can be nonzero. If the torque on an object is zero, then the rate of change of the angular momentum is zero but the angular momentum itself can be nonzero, indicating that choice (C) is incorrect. If the torque is nonzero, the magnitude of the angular momentum can be constant while its direction changes (think of a precessing gyroscope).
Diagnostic Test: Electricity and Magnetism
41. Given three capacitors with different capacitances, how many different equivalent capacitances can you obtain by using these capacitors either singly or in combinations of two or three?
(A) 5
(B) 8
(C) 11
(D) 14
42. Which of the following statements is true?
(A) Magnetic field lines have north and south poles as their sources.
(B) Magnetic field lines are tangent to the direction of the magnetic force on a moving charge.
(C) The magnetic force on a moving charge does not change the energy of the charge.
(D) A current carrying loop of wire tends to line up in an external magnetic field with the plane of the loop parallel to the direction of the field.
Answer Explanations
41. (D). Using all three we can have them in series, all in parallel or two in parallel and that combination connected in series to the third. There are 1+1+3 = 5 such combinations. There are three ways of choosing only one capacitor and not using the other two. There are 3 ways of choosing two in a series combination and 3 ways of choosing two in a parallel combination (not using the third capacitor at all). Thus, there are 5+3+3+3 = 14 different equivalent capacitances.
42. (C) Magnetic field lines form closed loops; they have no sources (Gauss’ Law of Magnetism, see chapter 15). So choice (A) is not correct. The magnetic force on a moving charge is given by F =qv x B. Thus, the force is perpendicular to the field and choice (B) is wrong. Because the force is perpendicular to the velocity, the magnetic field cannot do work on the charge and its energy is unchanged. Choice (C) is thus correct. Choice (D) is incorrect because a loop of current (a magnetic dipole) aligns with its plane perpendicular to the direction of the external field.
Practice Test 1: Mechanics
41. At a given point above the Earth’s surface, the gravitational acceleration is 5.4 m/s2. The height of this point above the Earth’s surface is (assume that the mass of the Earth is 5.98 x 1024 kg and the radius of the Earth is 6.38 x 103 km):
(A) 2200 km
(B) 2200 m
(C) 220 m
(D) 22 m
42. A 5.7 kg block attached to a spring executes simple harmonic motion on a frictionless horizontal surface. At time t=0 s, the block is located at x=-0.20 m, moving with velocity v=-0.80 m/s with acceleration a=4.1 m/s2. What is the value of the spring constant k?
(A) 98 N/m
(B) 20.5 N/m
(C) 117 N/m
(D)153 N/m
Answer Explanations
41. (B) When sphere #3 is brought close to #2, electrons on #2 will move towards the side of the sphere closest to #3, which has positive charge. This flow of electrons will make the side of #2 farthest from #3 positively charged. Connecting #1 and #2 with a wire then allows electrons to flow from #1 to the positively charged side of #2. Disconnecting the wire ends this flow and removing #3 leaves #2 negatively charged from the electrons that flowed to it across the wire. Sphere #1 is no longer neutral because of the electrons that have left it and it has a net positive charge.
42. (C) Choice (A) is not true. Only a spherical conductor will have uniform charge distribution on its surface. While a conductor in a static situation is an equipotential, the potential need not be zero, so choice (B) is not correct, while choice (C) is the correct answer. Choice (D) is also wrong; even if a conductor is hollow, the electric field inside will be zero. This is the basis for electric shielding and the Faraday cage.
Practice Test 1: Electricity and Magnetism
41. Two uncharged metal spheres, labeled #1 and #2, are mounted on insulating supports. The spheres are located near each other but are not touching. A third metal sphere carrying a positive charge is placed near sphere #2. Next, a copper wire is briefly connected between spheres #1 and #2 and then removed. Finally, the third sphere is removed. In this final state
(A) spheres #1 and #2 are still uncharged.
(B) sphere #1 carries positive charge and #2 carries negative charge.
(C) sphere #1 carries negative charge and #2 carries positive charge.
(D) spheres #1 and #2 both carry positive charge.
42.When there is a net static charge on a conductor with an irregular shape and no other charges present nearby,
(A) the charge will be uniformly distributed over the surface of the conductor.
(B) every point throughout the entire conductor will be at zero potential.
(C) every point throughout the entire conductor will be at constant potential but not necessarily zero.
(D) the electric field inside the conductor need not be zero if the conductor is hollow.
Answer Explanations
41. (B) When sphere #3 is brought close to #2, electrons on #2 will move towards the side of the sphere closest to #3, which has positive charge. This flow of electrons will make the side of #2 farthest from #3 positively charged. Connecting #1 and #2 with a wire then allows electrons to flow from #1 to the positively charged side of #2. Disconnecting the wire ends this flow and removing #3 leaves #2 negatively charged from the electrons that flowed to it across the wire. Sphere #1 is no longer neutral because of the electrons that have left it and it has a net positive charge.
42. (C) Choice (A) is not true. Only a spherical conductor will have uniform charge distribution on its surface. While a conductor in a static situation is an equipotential, the potential need not be zero, so choice (B) is not correct, while choice (C) is the correct answer. Choice (D) is also wrong; even if a conductor is hollow, the electric field inside will be zero. This is the basis for electric shielding and the Faraday cage.
Practice Test 2: Mechanics
41. A car traveling at 14.8 m/s skids to a stop in 39 m after the brakes are applied. How far would the car travel before stopping if its speed were 29.5 m/s when the brakes were applied?
(A) 39 m
(B) 78 m
(C) 156 m
(D) 312 m
42. A spinning ice skater is able to control her rotation speed by pulling in her arms. In this process which of the following quantities remains constant?
(A) Her angular momentum
(B) Her moment of inertia
(C) Her kinetic energy
(D) Her angular velocity
Answer Explanations
41. (C) The work-energy theorem says that the change in the car’s kinetic energy is the work done on it by the force of friction, i.e. 0-1/2mv2=uFNdcos180∘, where d is the distance traveled. Newton’s Second Law tells us that Thus, the distance traveled is proportional to the speed of the car squared. So, if the speed is doubled, then the distance is quadrupled and choice (C) is correct.
42. (A) Assuming that the ice has negligible friction, there is negligible external torque on her, so her angular momentum is conserved, i.e., it remains constant. Her moment of inertia decreases as she pulls in her arms as does her angular velocity. Her kinetic energy increases, though this may not be immediately obvious. While her angular velocity increases, her moment of inertia decreases. However, her kinetic energy is given by Thus, with her angular momentum constant, her kinetic energy increases with the increase in her angular speed
Practice Test 2: Electricity and Magnetism
41. Referring to question 40, the two spheres are now connected by a conducting wire which is then removed. The electric force on each sphere is then
(A) zero
(B) 10.8 N, repulsive
(C) 3.6 N, attractive
(D) 3.6 N, repulsive
42. An electron is released from rest at a distance of 0.09 m from a proton which is held at a fixed position in space. How fast will the electron be moving when it is 0.03 m from the proton?
(A) 75 m/s
(B) 106 m/s
(C) 130 m/s
(D) 1060 m/s
Answer Explanations
41. (D) When the spheres are connected by a wire, charge will flow until the two spheres have equal charge of -12The force is then repulsive and has magnitude
42. (B) Conservation of energy tells us that the change in the potential energy of the electron equals the negative of the change in its kinetic energy. The change in potential energy is given by times the change in the potential, where Thus, where and is the unknown velocity. Solving for we find choice (B)
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