AP® Physics 1 Unit 4 Review and Practice Test
AP® Physics 1 Unit 4 feels clearer with a focused linear momentum review that reinforces impulse, conservation, and collision setups exactly as the AP exam presents them. Brief recaps keep formulas and concepts sharp, while AP-style practice tests strengthen pacing, accuracy, and confidence for exam day.
Your AP Physics 1 Unit 4 Review Made Simple
Break down linear momentum with easy lesson videos, visual examples, and practice sets. This AP® Physics 1 Unit 4 review helps you study smarter and feel ready for test day.
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Learn AP Physics 1 Unit 4 topics like linear momentum through short, clear videos that break down the tough parts. Each lesson walks you through real examples, so you actually understand what’s happening, not just memorize steps.
Interactive Study Guides
Explore AP Physics 1 Unit 4 concepts like linear momentum with study guides that are easy to follow and actually helpful. You can review definitions, work through examples, and check your understanding as you go. Each guide is built to simplify tough ideas so you can study at your own pace.
AP Physics 1 Unit 4 Practice Test Questions for Linear Momentum
Question
A student measures the force exerted on a 0.5 kg lab cart with respect to time in two different sections, as shown in the graph. During which of the two sections does the lab cart experience a greater change in momentum?
| A. Section 1 | |
| B. Section 2 | |
| C. The changes in momentum for both sections 1 and 2 are equal. | |
| D. Neither section 1 nor 2 shows a change in momentum. |
Explanation
The change in momentum is equal to the area under the curve of a force vs. time graph. The area under the curve is given by the impulse-momentum equation:
Looking at the two sections individually gives:
where A1 represents the area under the curve for section 1, and
where A2 represents the area under the curve for section 2.
Therefore, the change in momentum value of 40N⋅s during section 1 is greater than the change in momentum value of 30N⋅s during section 2.
Question
A collision takes place between balls of mass m and 3m, as shown above. The balls are initially traveling at the same speed v0 and move together to the left with velocity vf after colliding. Which of the following compares the kinetic energy KE and momentum p of the two-ball system before and after the collision?
| A. KE0 = KEf; p0 = pf | |
| B. KE0 < KEf; p0 > pf | |
| C. KE0 > KEf; p0 = pf | |
| D. KE0 > KEf; p0 > pf |
Explanation
The momentum (p) of an object is a vector, defined as the product of the object's mass (m) and its velocity (v):
When objects interact with each other (eg, collide), each object experiences a change in momentum (Δp) over time Δt. The rate of change of momentum is equal to the net force (Fnet) acting on each object:
Collisions between objects can be described by considering each of the objects as parts of a system, with total momentum (ptotal) given by the sum of each object's momentum:
If zero external force (Fnet = 0) is exerted on the system, then there is conservation of total momentum:
In this question, the total momentum of the two-ball system before the collision (p0) is:
Since Fnet = 0, total momentum is conserved, and the final momentum after the collision (pf) is equal to p0:
Furthermore, the collision is perfectly inelastic since the balls move together after colliding. In an inelastic collision, some kinetic energy (KE) is lost (e.g., heat, sound), and the total kinetic energy KE0 before the collision must be greater than the total kinetic energy KEf after the collision, where KE0 is:
and KEf is:
Therefore, the collision of the two balls is described by the relationships:
KE0 > KEf p0 = pf
(Choice A) Total momentum is conserved, but since the collision is inelastic some KE is lost. Therefore, KE0 is not equal to KEf.
(Choice B and D) In these incorrect answers, initial momentum is greater than final momentum. Since there is no external force acting on the two-ball system, a difference in p before and after the collision is inconsistent with conservation of momentum.
Things to remember:
Total momentum is conserved in all collisions between objects that have zero external force exerted on the system. In perfectly inelastic collisions, objects stick together and their total kinetic energy is not conserved.
Question
Two carts with equal mass and equal speed collide head-on and undergo two separate collisions on a frictionless track. In collision A, the carts undergo an elastic collision. In collision B, the carts undergo an inelastic collision and stick together. Which of the following compares the magnitude of change in total kinetic energy ΔKE and the magnitude of change in total momentum ΔP during the two collisions?
| A. ; | |
| B. ; | |
| C. ; | |
| D. ; |
Explanation
The momentum P of a moving object is equal to the object's mass m multiplied by its velocity v:
Newton's second law of motion implies that the change in a system's total momentum ΔP over a time interval Δt is equal to the net external force Fext exerted on the object:
A collision involves an internal interaction between two objects over a time. Hence, the external force on the system is zero and total momentum is conserved:
In this question, the type of collision dictates whether kinetic energy (KE) is also conserved or not. In an elastic collision, no energy is lost due to the interaction of objects with each other, and in collision A, the total kinetic energy KE of the carts before and after the collision is equal:
Alternatively, in an inelastic collision energy is lost due to the interaction of objects with each other, and the total kinetic energy of the carts before and after the collision is not equal. Hence, the magnitude of change in kinetic energy is greater for collision B than collision A:
Therefore, it follows that ΔPA = ΔPB and the kinetic energy change for collision A is less than that for collision B.
(Choices A, B, and D) Momentum is conserved for both collisions. However, collision B is inelastic; hence the change in total kinetic energy is greater than the change in total kinetic energy for collision A.
Things to remember:
Momentum is conserved in all collisions, but kinetic energy is lost in inelastic collisions.
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Frequently Asked Questions (FAQs)
What are the main topics covered in AP Physics 1 Unit 4: Linear Momentum?
AP Physics 1 Unit 4 covers several key ideas that help you understand how objects move and interact during collisions. The topics include:
- Linear momentum: How mass and velocity combine to describe motion.
- Change in momentum and impulse: How forces acting over time affect motion.
- Conservation of linear momentum: How momentum stays constant in closed systems.
- Elastic and inelastic collisions: How objects bounce or stick together after impact.
These ideas show up in problems where objects collide, push apart, or change speed. You’ll often compare “before and after” motion to see how momentum shifts within a system. Understanding these concepts helps you break down real-life situations like sports impacts or vehicle collisions in a clear, predictable way.
If you prefer guided practice, UWorld’s AP Physics 1 Unit 4 videos and step-by-step explanations make these topics easier to understand. You can review examples, check your work, and build confidence before exam day.
How should I prepare for an AP Physics 1 Unit 4 exam?
Preparing for an AP Physics 1 Unit 4 exam works best when you study in a clear order: read, watch, and practice. Start by reviewing linear momentum and collision concepts in a study guide so you understand the basics before solving problems. Focus on definitions, formulas, and the big ideas behind momentum, impulse, and conservation.
Next, watch short lesson videos that walk you through examples step-by-step. Seeing the problems solved visually makes it easier to follow the logic and understand how changes in momentum happen in real situations. Videos also help connect the formulas to the actual physics behind them.
To bring everything together, practice with realistic AP Physics 1 Unit 4 questions that show you the types of problems you’ll face on test day. UWorld’s study guides, video lessons, and detailed explanations help you check your work, fix mistakes, and feel more confident with each session.
Are any free resources available for AP Physics 1 Unit 4?
Yes, there are free resources you can use to review AP Physics 1 Unit 4, and the best place to start is UWorld’s free trial. It gives you access to a sample of high-quality practice questions and explanations so you can see how linear momentum and collisions are tested. The free trial lets you explore the tools you’ll use throughout your prep without committing right away.
You can also check out free materials from the College Board, including sample questions and scoring guidelines. Khan Academy offers short videos and basic concept reviews that can help you refresh key ideas before diving into deeper practice. These resources are helpful for quick review or building a foundation.
For a more complete study experience, UWorld’s full AP Physics 1 course provides exam-level questions, video lessons, and study guides that break down tricky topics step-by-step. It’s a reliable way to strengthen your Unit 4 understanding and feel more prepared for test day.
What types of questions are on the AP Physics 1 Unit 4 test?
The AP Physics 1 Unit 4 test includes multiple-choice and free-response questions that focus on linear momentum, impulse, and collisions. You’ll see problems where objects collide, push apart, or change speed, and you’ll need to calculate momentum changes or apply conservation laws. Some questions are conceptual, while others require math, diagrams, or interpreting graphs.
FRQs often ask you to explain your reasoning, compare “before and after” motion, or justify why momentum is conserved in a system. You might break down elastic versus inelastic collisions or describe how impulse affects motion. These questions reward clarity and logical steps as much as correct calculations.
If you want to practice these question types, UWorld’s AP Physics 1 Unit 4 problems mirror the style and difficulty of real exam items. Each question includes a step-by-step explanation, helping you learn the reasoning, catch mistakes, and build confidence before test day.
How can I improve my score on the Free-Response Questions (FRQs) for Unit 4?
Improving your FRQ score on AP Physics 1 Unit 4 starts with knowing what the questions expect. FRQs usually ask you to explain momentum changes, show how impulse affects motion, or apply conservation of momentum to collisions. Focus on writing clear steps, labeling diagrams, and showing your reasoning instead of jumping straight to equations.
Practice breaking each problem into small parts: identify the system, write the momentum before and after, and decide whether the collision is elastic or inelastic. FRQs reward clear logic, organized work, and strong explanations, even if your math isn’t perfect. The key is showing why your approach makes sense.
To build these skills, UWorld’s AP Physics 1 Unit 4 explanations walk you through real FRQ-style problems with step-by-step reasoning. Reviewing these examples helps you understand how to structure your answers and score higher on test day.
What is the "Linear Momentum" unit's weight on the AP Physics 1 exam?
AP Physics 1 Unit 4, which focuses on linear momentum, usually makes up around 12 to 18 percent of the exam. This includes questions on impulse, momentum changes, and different types of collisions. The weighting can shift slightly each year, but Unit 4 is always a meaningful part of the test, especially in both multiple-choice and FRQ sections.
Because linear momentum connects with forces, motion, and energy, it tends to show up in questions that test your ability to analyze “before and after” situations. You may be asked to calculate momentum, compare collision types, or explain why momentum is conserved in a system. Understanding these ideas helps you handle a variety of problem types.
If you want a targeted review for this section, UWorld’s AP Physics 1 Unit 4 questions and explanations make the weighting easier to manage. You can focus on the topics that matter most and practice realistic problems that strengthen your confidence for test day.
Where can I find a good study guide for AP Physics 1 Unit 4?
You can find a strong study guide for AP Physics 1 Unit 4 by starting with UWorld, since it offers clear explanations of linear momentum, impulse, and collisions in one organized place. The study guide is built to walk you through definitions, formulas, and worked examples so you understand exactly how each idea connects to the exam.
While free resources like AP Classroom or Khan Academy can be useful for quick refreshers, they often give only surface-level summaries. They’re helpful when you want a basic overview but don’t always show the depth or reasoning needed for tougher problems.
For a fully exam-ready review, UWorld’s AP Physics 1 Unit 4 study guide pairs with videos and practice questions, giving you a complete system to learn concepts, test your understanding, and feel more confident on test day.
Can I find practice tests specifically for AP Physics 1 Unit 4?
You can find practice tests focused on AP Physics 1 Unit 4 if you look for resources that break down linear momentum, impulse, and collisions into exam-style questions. These sets usually include multiple-choice problems and short free-response tasks that match what you’ll see on test day. They’re helpful when you want a targeted review without working through an entire full-length exam.
Some educational sites offer unit-based quizzes or momentum-focused problem sets that let you practice at your own pace. These are great for checking your understanding, building confidence with calculations, and reviewing the logic behind momentum changes and collision outcomes.
If you want unit-specific tests with detailed explanations, UWorld offers practice questions built around AP Physics 1 Unit 4 topics. Each question shows you the reasoning step-by-step so you can learn the method, correct mistakes, and improve quickly before the exam.
Do I need to memorize formulas for AP Physics 1 Unit 4?
You don’t need to memorize every single formula for AP Physics 1 Unit 4, but you should be familiar with the core ones related to linear momentum, impulse, and collisions. Knowing what each formula represents and when to use it helps you move through problems faster and avoid simple mistakes. The test is more about understanding ideas than memorizing symbols.
Most Unit 4 questions focus on how momentum changes, how forces act over time, and how collisions behave in real situations. When you understand the meaning behind the formulas, you can concentrate on diagrams, direction, and interpreting the system instead of trying to recall equations under pressure.
If you want to build confidence using these key relationships, UWorld’s AP Physics 1 Unit 4 questions show how each concept works step-by-step. The explanations guide you through the logic behind every solution so you learn the reasoning, not just the final answer.
What skills matter most for AP Physics 1 Unit 4 questions?
The most important skills for AP Physics 1 Unit 4 involve understanding relationships between force, time, and motion. You’ll need to interpret diagrams, track direction, compare momentum before and after collisions, and explain your reasoning clearly. It’s less about memorizing facts and more about seeing how everything fits together.
Many questions ask you to analyze changes in momentum, decide whether momentum is conserved, or determine how objects move after an impact. Being able to read graphs, label systems, and organize your work makes these problems feel much more manageable. Logical steps matter as much as correct math.
To build these skills, UWorld’s AP Physics 1 Unit 4 questions and explanations model the type of thinking the exam expects. Working through these examples helps you understand what the graders look for and how to approach each problem with confidence.