Test Prep

# AP® Physics 1

Shmoop's Preparation for the AP® Physics 1 Exam

Couldn't recognize Newton's laws if they chucked an apple at your head? (We know it's a subject and doesn't have arms. Just go with it.) Come get your laugh and your learn on with Shmoop's guide to AP Physics 1.

In this guide, you'll learn

• concepts that appear in the first semester of an algebra-based intro…to physics course.
• how to model resistivity of matter at the next house party you attend…although we can't promise that it'll make you the most popular kid there. Definitely second most popular, though.

Like gravitational force, Shmoop will keep you grounded…in AP Physics 1 that is.

### In Shmoop's guide to AP Physics 1, you'll find

• a diagnostic exam to figure out where you're struggling before you even begin.
• two full-length practice exams that mimic the look and feel of the exam.
• answer explanations to figure out where you went wrong…or right.
• review of kinematics, gravity, energy conservation, and more.
• test-taking tips and strategies.

## The Details

### Big Idea 1: Properties of Objects and Systems

It may seem like a daunting task to identify the relevant properties of any type of matter. Don't worry: We've got your back. We want you to have every trick at your disposal for success. Here's a short trail of breadcrumbs in case you lose your way.

• Mass and charge are intrinsic characteristics of material. Only the President of Physics knows where they come from, and even Albert Einstein couldn't get that guy to return his calls. We handle these characteristics as they're identified in problem statements or empirical measurements and save the philosophical lines of questioning for Ancient Guys in White Robes and Sandals 101.
• When considering mass, how much of it is there? We mean matter-type mass, not the one that takes place on Sundays. In physics, mass is around pretty much all the time. If the mass isn't already given, why not? Is there a process happening that could tell us how much of this stuff is actually there?
• The mathematics of Big Idea 1 considers charge electrostatically. We may ask about a charged object's general direction of movement, but for the most part, we're concerned with amounts of charge and how systems tend toward neutrality.
• An item whose mass or charge is a given within a problem statement or set of measurements should be treated as an object. A system is the stuff outside the object that influences its motion. When the system-object distinction isn't clear, look for the component whose intrinsic characteristics are identified first and objectify the heck out of it.
• Things with relevant structures are systems. By "relevant," we mean that the structure lends itself to the motion of objects. An object with an alibi that places it outside of the system's influence at the time of interaction cannot be held accountable for interactions within that system. This argument works physically and in a court of law.

Please print this material out before using your highlighters. Parents are so unappreciative of the old computer-screen-marked-in-permanent-fluorescence gag.

### Big Idea 2: Fields in Space

Here's an In Case of Emergency List for Big Idea 2.

• A field is a force-carrying expanse that surrounds an object. Yes, it is a real thing that exhibits real effects; no personal summoning required. This isn't Obi-Wan Kenobi's Guide to Using The Force, but it'll do.
• Fields are physical, but we can't see them. If it helps, think of a field as mathematical construct first. If that doesn't work, imagine your classmates in their underwear.
• Fields follow the inverse square law. They dominate at distances that are very close to the source object, with their influence tapering off quickly as stuff gets further away from the source. This is why we often set your marshmallow on fire instead of getting it to that nice, brown roast.
• AP Physics 1 discusses gravitational fields. The field of a mass points inward, toward the center of the mass, as if to say, "It was him! He started the field!"
• Weight is just a measure of the planet's gravitational pull on our bodies. The easiest way to lose excess weight is to visit the moon, though it's not the most cost-effective method.

If these don't work, call the police! Actually, please don't. If you must, don't mention Shmoop.

### Big Idea 3: Object Interaction and Forces

The AP Physics 1 exam is quite the force to be reckoned with (heh heh), so pay close attention to this stuff.

• Forces are responsible for the motion of everything. Gravity pulls Earth around the Sun, electricity pushes current through personal electronics, and if we tied a thousand or so helium-filled balloons to Papa Shmoop's chair, the buoyant force may allow him to achieve liftoff. Happy floating!
• Newton's laws of motion take place in inertial reference frames. These points of observation are either stationary or moving at a constant speed. We're out of luck if we happen to be seated on an accelerating roller coaster the next time we want to collect data for a motion experiment.
• There are a lot of definitions to power through before we can really get started, but we've probably seen at least one of them before. Some of them are familiar—not too familiar, though. Respect our boundaries, definitions.
• Thou shalt become BFFs with vector algebra. Forces are directional, so they're represented by vectors. It's a thing.
• A torque is a linear force with a twist—literally. Torque is about spin. Without a little daily torque, we wouldn't be able to ride, drive, or log-roll our way to the Lumberjack World Championship.

Question: Could a force and a torque mate to produce a forque? Perhaps, but we wouldn't need those new forques if we did the dishes when Mama Shmoop asked.

### Big Idea 4: System Interactions and Changes

As you learn this ancient art, bear these secrets in mind.

• A system is a collection of objects whose motion depends on the internal structure of the system. The phrase "What goes up must come down" would be useless without systematic influences like gravity or the enchanted makes-things-fall-to-the-ground physics unicorn.
• System structure arises from the system's distribution of objects and force fields. Locations, distances, and field values matter. Also, in matters of matter, matter matters.
• The definitions we're about to encounter may look familiar. It's not because they all took selfies and posted them on Instagram. When referenced from the center of mass, system kinematics look an awful lot like object kinematics.
• Ever get tired of hearing about your "potential?" You're in luck! AP Physics 1 only ever discusses system and object potentials. Potential energy is "stored" energy that may be exchanged for kinetic energy during motion with systematic influences. Objects don't have potential energy without system-derived forces. Therefore, only systems may contain potential energy. Be warned: Your potential may make a reappearance when you next meet with your guidance counselor.
• Vectorially, torque is represented by a spinning arrow in space. We already know that it's put there by a force applied over a momentum arm. What we don't know is why it can't be spelled like pork, cork, and fork.

Grumpy Cat is the king of potential energy. He doesn't seem to do very much, but he could if he wanted.

### Big Idea 5: Changes and Conservation Laws

We have no idea what the President of Physics really intended when he designed nature to act this way, but we're like 80 percent sure he wanted 2015 C.E. AP Physics 1 students to learn about it for entrance into a great university program.

• Conservation laws are the backbone of all physical processes. They're older than Neil Diamond's Greatest Hits. Nearly every equation you've set eyes upon throughout this guide boils down to a conservation law.
• The most important conserved quantities are energy, charge, mass, and momenta. They are of ludicrous significance in Big Idea 5 and, arguably, throughout the rest of science. This stuff will conserve like a right-wing environmentalist! Get it? Because they're a conservative conservationist? Insert eye roll here.
• Electricity is a vast concept with many specialized nuances in advanced physics courses. Later in life, you will be fed super-sized portions of an electric field and special relativity sandwich. For now, in AP Physics 1, charge and energy conservation laws will let us take a peek at the functioning of basic circuits.
• Now comes the time when we will thoroughly discuss the subject that inspired you to take AP Physics 1: human reproduction. Err, sorry, we mean collisions. Nothing is more exciting to a budding physicist than hits, run-ins, explosions, and other sudden transfers of energy and momentum.
• The bulk of the angular momentum discussion lies here. If its treatment in Big Idea 4 was unsatisfying, don't worry. We've got plenty of angular momentum deliciousness to treat you to.

Big Idea 5 is ripe for attention if you're desperately cram-studying this material the week of the exam. (What? You? Never.) In fact, concepts from this idea pop up in the rest of the Big Ideas. This is where we'll tie together the object/system distinction, potential energy fields, object forces, and system dynamics into one beautiful web of physicality and consequence.

### Big Idea 6: Waves

We can wave goodbye to angular momentum, at least for now. The physics puns are staying, however.

• The AP Physics 1 exam will only deal with mechanical waves. All of that electromagnetic wave junk is reserved for AP Physics 2. Lucky you!
• All mechanical waves require a medium for propagation. Whether it's the ocean, a string, or the Tacoma Narrows Bridge back in 1940, something must be disturbed for wave-like motion to happen.
• There are longitudinal waves and then there are transverse waves. Longitudinal waves push things through the medium. Transverse waves cause stuff to bob up and down in the same spot as if to say, "Look at me! I'm moving but I'm not really going anywhere! Wheee!"
• Most of the waves you will see here are periodic. That means that you'll be dealing with terms like frequency, wavelength, and period again. No, we won't be re-inventing the simple harmonic oscillator problems. However, if those problems were never your bag to begin with, these will probably give you a better understanding.
• Waves are capable of interference. Interference is the property that allows them to combine with one another in basic and exotic ways. It's a lot like the square-dancing lesson that your parents had to take in grade school physical education.

Are you ready to get loosey-goosey and do a funky, interpretative dance for the following models and sample problems? Don't forget to stretch.

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