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College Physics

Introduction to One-Dimensional Kinematics

College PhysicsIntroduction to One-Dimensional Kinematics

Photo of a bird in flight.
Figure 2.1 The motion of an American kestrel through the air can be described by the bird’s displacement, speed, velocity, and acceleration. When it flies in a straight line without any change in direction, its motion is said to be one dimensional. (credit: Vince Maidens, Wikimedia Commons)

Chapter Outline

2.1 Displacement
  • Define position, displacement, distance, and distance traveled.
  • Explain the relationship between position and displacement.
  • Distinguish between displacement and distance traveled.
  • Calculate displacement and distance given initial position, final position, and the path between the two.
2.2 Vectors, Scalars, and Coordinate Systems
  • Define and distinguish between scalar and vector quantities.
  • Assign a coordinate system for a scenario involving one-dimensional motion.
2.3 Time, Velocity, and Speed
  • Explain the relationships between instantaneous velocity, average velocity, instantaneous speed, average speed, displacement, and time.
  • Calculate velocity and speed given initial position, initial time, final position, and final time.
  • Derive a graph of velocity vs. time given a graph of position vs. time.
  • Interpret a graph of velocity vs. time.
2.4 Acceleration
  • Define and distinguish between instantaneous acceleration, average acceleration, and deceleration.
  • Calculate acceleration given initial time, initial velocity, final time, and final velocity.
2.5 Motion Equations for Constant Acceleration in One Dimension
  • Calculate displacement of an object that is not accelerating, given initial position and velocity.
  • Calculate final velocity of an accelerating object, given initial velocity, acceleration, and time.
  • Calculate displacement and final position of an accelerating object, given initial position, initial velocity, time, and acceleration.
2.6 Problem-Solving Basics for One-Dimensional Kinematics
  • Apply problem-solving steps and strategies to solve problems of one-dimensional kinematics.
  • Apply strategies to determine whether or not the result of a problem is reasonable, and if not, determine the cause.
2.7 Falling Objects
  • Describe the effects of gravity on objects in motion.
  • Describe the motion of objects that are in free fall.
  • Calculate the position and velocity of objects in free fall.
2.8 Graphical Analysis of One-Dimensional Motion
  • Describe a straight-line graph in terms of its slope and y-intercept.
  • Determine average velocity or instantaneous velocity from a graph of position vs. time.
  • Determine average or instantaneous acceleration from a graph of velocity vs. time.
  • Derive a graph of velocity vs. time from a graph of position vs. time.
  • Derive a graph of acceleration vs. time from a graph of velocity vs. time.

Objects are in motion everywhere we look. Everything from a tennis game to a space-probe flyby of the planet Neptune involves motion. When you are resting, your heart moves blood through your veins. And even in inanimate objects, there is continuous motion in the vibrations of atoms and molecules. Questions about motion are interesting in and of themselves: How long will it take for a space probe to get to Mars? Where will a football land if it is thrown at a certain angle? But an understanding of motion is also key to understanding other concepts in physics. An understanding of acceleration, for example, is crucial to the study of force.

Our formal study of physics begins with kinematics which is defined as the study of motion without considering its causes. The word “kinematics” comes from a Greek term meaning motion and is related to other English words such as “cinema” (movies) and “kinesiology” (the study of human motion). In one-dimensional kinematics and Two-Dimensional Kinematics we will study only the motion of a football, for example, without worrying about what forces cause or change its motion. Such considerations come in other chapters. In this chapter, we examine the simplest type of motion—namely, motion along a straight line, or one-dimensional motion. In Two-Dimensional Kinematics, we apply concepts developed here to study motion along curved paths (two- and three-dimensional motion); for example, that of a car rounding a curve.

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