How to Understand Classical Physics

Three Parts:Learning Newton’s Laws of Motion and ConservationUnderstanding the Motion of ObjectsExpanding your Knowledge

Classical physics is the study of motion, projectiles, pulleys, and the planets. It mainly deals with the movement of large objects through space at a relatively low slow speeds.[1] Classical physics deals with the mechanics of an object’s motion in response to a force. Because of this, classical physics is often referred to simply as mechanics or kinematics.

Part 1
Learning Newton’s Laws of Motion and Conservation

  1. Image titled Understand Classical Physics Step 1
    Define Newton’s first law of motion. Newton’s first law tells us that any object in motion will continue to move in the same direction with the same speed unless another force acts on it to change its motion. If an object is stationary, it will remain stationary.[2]
    • This first law is sometimes referred to as the law of inertia.[3]
    • This law states that an object moves with a constant velocity (speed and direction) unless there is a nonzero (unbalanced) net force acting on it. An object that is not moving has a net force of zero acting on it.
  2. Image titled Understand Classical Physics Step 2
    Understand Newton’s second law of motion. As the force acting on an object increases, the acceleration of the object increases. Force alone does not determine the acceleration of an object; the object’s mass also plays a critical role. The larger the mass of an object, the slower it will accelerate.[4]
    • This relationship can be explained using the formula F = ma where “F” is the force acting on the object, “m” is the mass of the object, and “a” is the acceleration of the object.
    • Another way to think about this law is that an object will not accelerate unless there is an unbalanced (or net) force acting on it.[5]
  3. Image titled Understand Classical Physics Step 3
    Learn Newton’s third law of motion. The third law states that every action has an equal and opposite reaction.[6] When a force acts on an object, there is a force of the exact same magnitude that pushes back in the opposite direction to the original force.
    • For example, when you sit down on a bench, you are exerting a downward force on the bench, but the bench is exerting an equal upward force on you.[7]
    • This law states that all forces come in pairs.
  4. Image titled Understand Classical Physics Step 4
    Know the laws of conservation of energy, momentum, and angular momentum. Conservation of energy states that “energy can be neither created nor destroyed.” In other words, energy remains constant in an isolated system. The same goes for momentum and angular momentum: in an isolated system momentum and angular momentum remain constant.[8]
    • It’s important to note that an isolated system is one in which there are no outside forces acting on it. In reality, an isolated system doesn’t really exist, but it is a useful model to describe the basic principles of the physical laws of nature.

Part 2
Understanding the Motion of Objects

  1. Image titled Understand Classical Physics Step 5
    Study the derivation of the basic equations. There are four basic equations that describe the motion of an object in terms of time (t), velocity (vf: final velocity; vi: initial velocity), acceleration (a), and displacement (d).[9] These are known as the kinematic equations and can be rearranged in various ways to solve for the desired variable.[10] Being able to derive these equations on your own will solidify your understanding of these concepts.
    • Recreate some basic physics labs at home and try to derive the equations from the data you have collected.
    • The basic kinematics equations are:
      • d = vit + ½at2
      • vf2 = vi2 + 2ad
      • vf = vi + at
      • d = (vi + vf)/2 * t
  2. Image titled Understand Classical Physics Step 6
    Define a vector. A vector is a quantity commonly used in math and physics that has both a magnitude and a direction.[11] The magnitude defines the “length” of the motion. When talking about velocity, the magnitude is the speed the object is moving. The direction the object moves defines the second component of the vector, direction.
    • When objects are in motion they generally move in one direction at a specific rate. They may be moving at a constant velocity or accelerating, but in either case, the motion is said to have both a magnitude and direction; therefore, its motion is a vector.[12]
  3. Image titled Understand Classical Physics Step 7
    Draw diagrams of the problem. Physics can be very abstract, but the best way to get to the root of the problem is to draw it out. Sketch a basic picture of what’s happening in the problem described and then add in all of the forces that exist.[13]
    • Forces are vectors so remember to draw them using an arrow with both a magnitude and direction.
    • Don’t forget about unseen forces such as the force of gravity, the friction force, and the normal force (the force that acts against an object resting on it).[14]
  4. Image titled Understand Classical Physics Step 8
    Practice with some examples. The best way to learn something is to dive right in. Try your hand at some basic problems to check your understanding. To solve any problem draw the diagram, write the givens, determine what you’re solving for and apply the correct equation to solve for your unknown.[15]
    • For example: Find the distance it takes for a car traveling at 25 m/s to stop using an acceleration of -9 m/s2.
    • Sketch a picture of the car, drawing arrows to represent the direction of travel.
    • Write down the knowns: vf = 0 m/s, vi = 25 m/s, a = -9 m/s2, d = ?
    • Identify the relevant equation: vf2 = vi2 + 2ad
    • Plug in the knowns: 02 = 252 + 2(-9)(d)
    • Solve for d: d = (02 - 252)/-18 = 34.72 m
    • The car traveled 34.72 meters before stopping.

Part 3
Expanding your Knowledge

  1. Image titled Understand Classical Physics Step 9
    Read a beginner’s physics textbook. If you really want to dive into classical physics, buy a beginner’s textbook and start reading.[16] Simply reading the concepts will not be enough to really understand. You must also review the sample problems and try your hand at some of the questions at the end of each chapter.
    • Take the time to process the derivations of the basic equations of motion and truly understand why they work before you move onto the next concept.
  2. Image titled Understand Classical Physics Step 10
    Take an online physics course. Reading a textbook on your own might not be enough for you to gain the depth of knowledge you’d like in physics. There are many open courseware and online courses you can take related to physics.[17][18] Many of these courses have assignments to check your understanding and forums to discuss the work.
    • These types of courses are also easy to fit into your schedule as you can work on the material when you have the time.
  3. Image titled Understand Classical Physics Step 11
    Experiment and do practice problems to check your understanding. Physics is a subject best learned through hands-on activities and solving practice problems. Do some basic experimenting and see if you can derive the equations based on your data. Answer all of the questions at the end of each chapter and check your solutions.
    • Seek out more problem sets online for concepts that are more troublesome than others.
    • Physics builds upon itself, so continue to do practice problems until you feel that you have mastered the concept before moving on to the next one.
  4. Image titled Understand Classical Physics Step 12
    Sign up for a basic physics class at a local college. If you work best in a classroom setting, check out the courses available at your local community college. Choose a course with a well-rated professor during a time that fits well into your schedule. Taking a course just because you’re curious about the material can be really fun and you’ll be more likely to focus on the work and truly learn the subject.
    • Take advantage of office hours and open lab times to discuss concepts that may be causing you trouble.

Article Info

Categories: Classical Mechanics