# AP Test - Physics

## The Basics

AP Physics B is supposed to be equivalent to a Category B (as opposed to a Category A or C) year-long introductory college course with lab in physics. A Category B physics course often provide a foundation in physics for students pursuing the life sciences, medicine, geology, or another field not directly related to science. It is non-calculus-based and utilizes algebra and trigonometry. It covers Newtonian mechanics, fluid mechanics and thermal physics, electricity and magnetism, waves and optics, and atomic and nuclear physics. A breakdown of the proportion of each topics covered on the AP test is given below. For an even more detailed breakdown, see attached pages below.

Topic |
Percent |
---|---|

Newtonian Mechanics |
35% |

Fluid Mechanics and Thermal Physics |
15% |

Electricity and Magnetism |
25% |

Waves and optics |
15% |

Atomic and Nuclear Physics |
10% |

Section |
Type |
# of Qs |
% of Final Score |
Time |
---|---|---|---|---|

1 |
Multiple Choice |
70 |
50% |
90 minutes |

2 |
Free Response |
6 to 7 |
50% |
90 minutes* |

*Each exam will change how long certain free response questions are. Read the directions on the exam for a guideline on how much time you should spend on each question. For example, the directions of the 2012 exam were: “Answer all seven questions, which are weighted according to the points indicated. The suggested times are about 11 minutes for answering each of Questions 2, 3, 4, 6, and 7 and about 17 minutes for answering each of Questions 1 and 5.”

The test is 3 hours long and contains 2 parts: multiple choice and free response. Each section takes 90 minutes long and is worth 50% of the final exam grade.

Section 1 contains 70 multiple-choice questions, which test the breadth of the student’s knowledge and understanding of physics. This means that students have about 77 seconds per question. Scores are based on the total number of questions answered correctly. There is no penalty for incorrect or unanswered questions.

Section 2 contains 6 or 7 free response questions, which test the student’s grasp on applying those physics principles to more in-depth problems. Typically one of these is a laboratory-based question. These laboratory-related questions may ask students to design experiments, analyze data, analyze error, and communicate results. Students should spend 11 to 17 minutes on each question, depending on the length of that specific problem.

Calculators are not permitted in the multiple-choice section, but a scientific, programmable, or graphing calculator is allowed on the free-response section. In both sections, students are provided with an info table and a formula sheet, both referenced below. The info sheet contains

*Formula Sheet: *

http://3.bp.blogspot.com/-Rslh1ZZVoVY/UQ_o9Fp_PcI/AAAAAAAAAAQ/tpwK0rDLq_w/s1600/AP+Physics+B+Equations+2012.JPG

Score |
2010 |
2011 |
2012 |
---|---|---|---|

5 |
14.80% |
16.40% |
16.30% |

4 |
18.50% |
19.20% |
19.30% |

3 |
26.10% |
25.90% |
26.40% |

2 |
18.60% |
17.30% |
16.80% |

1 |
21.90% |
21.30% |
21.30% |

Mean |
2.86 |
2.92 |
2.93 |

Number of Students |
67312 |
75648 |
80584 |

- The course can help students prepare for the SAT Subject Test in Physics.
- Students must attend labs, because free-response questions are often based on those lab experiments.
- Know key words: justify, explain, calculate, what is, determine, derive, sketch, and plot in order to maximize points and to avoid including irrelevant material in the answer.
- Justify, explain: support answer with prose, equations, calculations, diagrams, or graphs
- Calculate: show work, algebraic and/or numerical
- What is, determine: work does not necessarily need to be explicitly shown to obtain full credit
- Derive: begin answers with one or more fundamental equations, such as those given on the formula sheet
- Sketch: graph that illustrates trends, with slope, curvature, intercepts, or asymptotes
- Plot: graph with scale and units

- It is more advantageous to take the AP Physics B exam than the AP Physics C exam if the student wants to pursue a non-engineering field. Credit for AP Physics B will also provide the student with an opportunity to meet a basic science requirement in favor of an accelerated course.
- Be wary that certain colleges, like Johns Hopkins University, will not accept AP Physics B credits. Instead, a calculus-based AP Physics C is required to obtain AP credits.
- Link to 1998 full exam: http://apcentral.collegeboard.com/apc/public/repository/254387_1998_PhysicsB_RE.pdf
- Mark down the date of the exam: May 12, 2014

Note that AP Physics B is scheduled for discontinuation with the last administration in May 2014. The reason given is that it “encourages cursory treatment of important topics in physics.” It will be replaced with AP Physics 1 and AP Physics 2 beginning in the 2014-2015 school year. Both of the replacements will be year-long algebra-based courses. AP Physics 1 is equivalent to a first-semester college course, and it covers Newtonian mechanics, work, energy, power, mechanical waves and sound, and electric circuits. AP Physics 2 is equivalent to a second-semester college course, and it covers fluid mechanics, thermodynamics, electricity and magnetism, optics, and atomic and nuclear physics.

- Newtonian Mechanics (35%)
- Kinematics (including vectors, vector algebra, components of vectors, coordinate systems, displacement, velocity, and acceleration) (7%)
- Newton’s laws of motion (9%)
- Work, energy, power (5%)
- Systems of particles, linear momentum (4%)
- Circular motion and rotation (4%)
- Oscillations and gravitation (6%)

- Fluid Mechanics and Thermal Physics (15%)
- Fluid Mechanics (6%)
- Temperature and heat (2%)
- Kinetic theory and thermodynamics (7%)

- Electricity and Magnetism (25%)
- Electrostatics (5%)
- Conductors, capacitors, dielectrics (4%)
- Electric circuits (7%)
- Magnetic Fields (4%)
- Electromagnetism (5%)

- Waves and Optics (15%)
- Wave motion (including sound) (5%)
- Physical optics (5%)
- Geometric optics (5%)

- Atomic and Nuclear Physics (10%)
- Atomic physics and quantum effects (7%)
- Nuclear physics (3%)

- An object is thrown with a horizontal velocity of 20 m/s from a cliff that is 125 m above level ground. If air resistance is negligible, the time that it takes the object to fall to the ground from the cliff is most nearly:
- 3 s
- 5 s
- 6 s
- 12 s
- 25 s

*Questions 2-3*

A 2 kg block, starting from rest, slides 20 m down a frictionlessinclined plane from X to Y, dropping a vertical distance of 10 m as shown above.

- The magnitude of the net force on the block while it is sliding is most nearly
- 0.1 N
- 0.4 N
- 2.5 N
- 5.0 N
- 10.0 N

- The speed of the block at point Y is most nearly
- 7 m/s
- 10 m/s
- 14 m/s
- 20 m/s
- 100 m/s

- An ideal monatomic gas is compressed while its temperature is held constant. What happens to the internal energy of the gas during this prcess, and why?
- It decreases because the gas does work on its surroundings.
- It decreases because the molecules of an ideal gas collide
- It does not change because the internal energy of an ideal gas depends only on its temperature.
- It increases because work is done on the gas.
- It increases because the molecules travel a shorter path between collisions.

Link to more free response questions and answers: http://apcentral.collegeboard.com/apc/members/exam/exam_information/2007.html

- Block A of mass 2.0 kg is pulled along a horizontal table by a force of 15 N, which is applied by a light string that passes over a light frictionless pulley, as shown above. The coefficient of kinetic friction between the block and the surface is 0.25.

- On the dot below, which represents the block, draw and label the forces (not components) that act on the block as it is pulled across the table.

- On the dot below, which represents the block, draw and label the forces (not components) that act on the block as it is pulled across the table.

- Calculate the magnitude of the acceleration of the block.

The applied force is removed. Block*B*of mass 1.5 kg is now attached to the string, as shown above. The system is released from rest so that the 1.5 kg box descends and the 2.0 kg block is again pulled across the table.

- Calculate the acceleration of the 1.5 kg block as it descends.

- Calculate the tension in the string connecting the two blocks.

- Calculate the distance that the 1.5 kg block descends in 0.40 s.

- If this system is set up in a laboratory and the acceleration of the 1.5 kg block is experimentally determined, the experimental value is found to be smaller than the value calculated above. If the given value for the coefficient of friction is correct and air resistance is negligible, explain briefly, but specifically, why the experimental value of the acceleration is smaller.

##### Sample Questions (Multiple Choice)

1. b. 5 s

2. e. 10.0 N

3. c. 14 m/s

4. c. It does not change because the internal energy of an ideal gas depends only on its temperature.

##### Sample Questions (Free Response)

**1a **

**1b**

Friction = F_{f}= µFN

Since F_{N} = mg (normal force equals the weight),

F_{f} = µmg = 0.25*2*9.8 = 4.9 N

Newton’s second law of motion: ∑F = ma

∑F = ma

(15 – F_{f}) = ma

(15 – 4.9) = 2a

10.1 = 2a

a = (10.1)/2 = 5.05 m/s^{2}

**1c**

Forces on block A in the x-direction: ∑F = m_{A}a = tension - friction

Forces on block B in the y-direction: ∑F= m_{B}a =m_{B}g – tension

Combine the two linear relationships: (m_{A}+ m_{B})a = m_{B}g – friction

→ (2.0 + 1.5)a = 1.5*9.8 – 0.25*2.0*9.8

→ a = 2.8 m/s^{2}

**1d**

m_{A}a = tension - friction = tension - µm_{A}g

tension = m_{A}(a + µg) = 2.0(2.8 + 0.25*9.8) = 10.5 N

**1e**

Δy = 1/2 at^{2} = 1/2 *2.8*0.402= 0.22 m

**1f**

The measured value of the acceleration was altered because:

- The pulley has an appreciable amount of friction in the bearings
- The string has an appreciable mass
- The pulley has an appreciable rotational inertia
- A small uphill incline exists in the horizontal surface

The measured value of the acceleration was smaller than the theoretical value because:

- The friction in the bearings of the pulley does negative work on the system, leaving less energy available for the system’s kinetic energy. This will result in a slightly smaller final velocity and therefore a slightly smaller acceleration than the theoretical value.
- The slightly inclined surface creates a small downward component of gravity, which works in opposition to the acceleration. This small opposing force will create a smaller net force and a decrease in the measured acceleration of block B.