Free Body Diagrams AP physics

In summary, The speaker is a high school student seeking help with AP calculus and gen physics. They are specifically struggling with drawing Free body diagrams and plugging equations into each other to solve problems. They are also looking for good resources with worked out problems and answers. The key to understanding FBDs is to remember to include all real forces and to properly express acceleration in terms of the chosen coordinate system.
  • #1
Hey everyone hows it going? I am not sure if this is the right place to be posting this question, but hopefully it is. My names Shawn and I am a senior in high school. I currently have AP calculus and gen physics, and I plan on taking the AP calculus test (ab) and hopefully the physics AP test, but I am not sure which one to take? Has anyone here taken either? I have borrowed an AP physics book ( Princeton review) and have been teaching it to myself. I think I am getting the concepts and everything but get lost a little here and there. Right now I am reading about Rotational Motion, but I am lost on drawing a Free body diagram. I can draw them right most of the time, but when it comes to putting it into the equation Fnet=ma that's where i get lost..So what should i be asking myself before i attempt to put it into the equation?. So any help on that would be greatly appreciated! Also i am having a tough time on the free response questions after every chapter, i can do the multiple choice questions with a little effort,but get stumped at the free response. After I see it done i always say "oh why didn't i think of that?". I am just having a hard time plugging equations into other equations into other equations etc to find what i need. Also one last thing, i learn best by doing problems so if you know of any good sites with problems AND ANSWERS with it worked out that would be awesome! Thanks for taking the time to help me!
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  • #2
FBDs are not really complicated if you remember to include all of the REAL forces that act on the body, and don't include any non-forces, such as mass*acceleration terms. Real forces include things like gravity forces, friction forces, contact (normal) forces between bodies, applied forces, and pressure forces such as buoyancy. These are the terms that go into the sum of forces.

The other side of Newton's second law, the mass*acceleration term requires that you have a proper understanding of how to express the acceleration in the coordinate system you are using.
  • #3

Hi Shawn,

It's great to hear that you are taking on the challenge of self-teaching AP physics! Free body diagrams are an important tool in understanding and solving problems in physics. Before attempting to put it into the equation Fnet=ma, there are a few things you should ask yourself:

1. What are the forces acting on the object? Identify all the forces, including gravity, normal force, friction, tension, etc.

2. What are the directions of these forces? Draw arrows representing the direction and magnitude of each force on your free body diagram.

3. Are there any forces canceling each other out? For example, if an object is on a flat surface, the normal force will cancel out the force of gravity in the vertical direction.

4. Are there any forces causing rotation? If so, you will need to consider torque in addition to forces in your equations.

5. Is the object in equilibrium or is it accelerating? If it is in equilibrium, the sum of all forces should equal zero. If it is accelerating, the sum of all forces should equal the mass of the object multiplied by its acceleration.

As for finding good practice problems, I recommend checking out past AP physics exams and the College Board's official AP physics practice questions. These will give you a good idea of the types of questions that may appear on the AP exam. Additionally, Khan Academy and Physics Classroom are great online resources for practice problems with solutions.

Remember, practice makes perfect! Keep working at it and don't be afraid to ask for help when needed. Good luck on your AP exams!

1. What is a free body diagram?

A free body diagram (FBD) is a diagram that represents the forces acting on an object without considering its surroundings. It is a visual representation of all the external forces acting on an object and their direction.

2. Why are free body diagrams important in AP physics?

Free body diagrams are important in AP physics because they help visualize and analyze the forces acting on an object, which is essential in understanding the principles of mechanics and solving problems involving forces and motion.

3. How do you draw a free body diagram?

To draw a free body diagram, first identify the object and all the forces acting on it. Then, draw a dot or a box to represent the object and draw arrows to represent the magnitude and direction of each force. Label each force with its name and use a coordinate system to indicate the direction.

4. What are the key components of a free body diagram?

The key components of a free body diagram include the object, the forces acting on the object, and a coordinate system to indicate the direction of the forces. It is also important to label each force with its name and use accurate and proportional arrows to represent the magnitude and direction of the forces.

5. Can you use free body diagrams to solve any physics problem?

Yes, free body diagrams can be used to solve most physics problems involving forces and motion. They provide a visual representation of the problem and help in identifying all the forces at play. However, in some advanced physics problems, other diagrams or equations may also be needed in addition to free body diagrams.

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