2.6 Problem-Solving Basics for One-Dimensional Kinematics

3 min readjune 18, 2024

One-dimensional is all about describing motion along a straight line. It's the foundation for understanding how objects move, using concepts like , acceleration, and .

In this section, we'll dive into problem-solving strategies for one-dimensional motion. You'll learn how to break down problems, choose the right equations, and interpret your results to master these fundamental physics concepts.

Problem-Solving Strategies for One-Dimensional Kinematics

Strategies for one-dimensional motion

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  • Identify known quantities and unknown variables
    • Gather given information from problem statement (, acceleration, time)
    • Determine quantity to solve for (, )
  • Draw diagram or sketch of scenario
    • Represent object as (ball, car)
    • Establish with origin and positive direction (, right is positive)
    • Label relevant positions, distances, or displacements (, )
  • Choose appropriate kinematic equation based on known and unknown quantities
    • v=v0+atv = v_0 + at relates velocity, initial velocity, acceleration, and time
    • Δx=v0t+12at2\Delta x = v_0t + \frac{1}{2}at^2 relates displacement, initial velocity, acceleration, and time
    • v2=v02+2aΔxv^2 = v_0^2 + 2a\Delta x relates final velocity, initial velocity, acceleration, and displacement
  • Solve equation for unknown variable
    • Substitute known quantities into chosen equation (values for v0v_0, aa, tt)
    • Perform algebraic manipulations to isolate unknown variable (solve for vv, Δx\Delta x)
  • Check units of solution to ensure consistency with quantity being solved for (m/s for velocity, m for displacement)

Evaluating kinematics solutions

  • Verify solution has correct sign
    • Positive displacement or velocity indicates motion in positive direction (moving right)
    • Negative displacement or velocity indicates motion in negative direction (moving left)
  • Check if magnitude of solution is within reasonable range
    • Compare solution to typical values for similar scenarios (car velocity vs. walking velocity)
    • Consider physical limitations or constraints (maximum speed of object)
  • Assess whether solution makes sense in context of problem
    • Reflect on implications of solution for given scenario (distance traveled in given time)
    • Identify contradictions or inconsistencies with problem statement (object reaching destination too quickly)

Interpretation of kinematic equations

  • Velocity-time equation (v=v0+atv = v_0 + at)
    • Describes velocity (vv) of object at given time (tt)
    • Initial velocity (v0v_0) is velocity at time t=0t = 0 (starting velocity)
    • Acceleration (aa) is constant rate of change of velocity (speeding up or slowing down)
    • can be calculated at any specific point in time using this equation
  • Position-time equation (Δx=v0t+12at2\Delta x = v_0t + \frac{1}{2}at^2)
    • Describes change in position (Δx\Delta x) of object over time (tt)
    • Initial velocity (v0v_0) affects position linearly with time (constant velocity term)
    • Acceleration (aa) affects position quadratically with time (accelerated motion term)
  • Velocity-displacement equation (v2=v02+2aΔxv^2 = v_0^2 + 2a\Delta x)
    • Relates final velocity (vv) to initial velocity (v0v_0), acceleration (aa), and displacement (Δx\Delta x)
    • Useful when time is not explicitly given or required (connecting velocities and displacement)
  • Analyze equations to determine effect of changing initial conditions or parameters
    1. Increasing initial velocity (v0v_0) results in greater final velocity and displacement (faster motion)
    2. Increasing acceleration (aa) results in greater change in velocity and larger displacement (more rapid change in motion)

Additional Kinematic Concepts

  • : A coordinate system used to describe the motion of objects, essential for defining position and velocity
  • : The total displacement divided by the total time, useful for describing overall motion
  • : The path an object follows through space, which in one-dimensional motion is a straight line
  • : A special case of motion where an object is subject only to gravitational acceleration, neglecting air resistance

Key Terms to Review (26)

Average velocity: Average velocity is the total displacement divided by the total time taken for that displacement. It is a vector quantity that indicates both magnitude and direction.
Average Velocity: Average velocity is the ratio of the total displacement of an object to the total time taken to cover that displacement. It represents the overall speed of an object's motion over a given time interval, providing a measure of how fast an object moves on average during that period.
Coordinate System: A coordinate system is a mathematical framework used to uniquely identify the position of a point or an object in space. It provides a systematic way to describe the location of an entity relative to a defined origin and a set of reference axes.
Displacement: Displacement is a vector quantity that refers to the change in position of an object. It has both magnitude and direction, indicating how far and in what direction the object has moved from its initial position.
Displacement: Displacement is the change in position of an object, measured from a reference point or origin. It describes the straight-line distance and direction an object has moved, without regard to the path taken.
Final Position: Final position refers to the ending location or point reached by an object or particle at the conclusion of a motion or movement in one-dimensional kinematics. It is the ultimate destination or resting place of the object after a specified time interval or distance traveled.
Final Velocity: Final velocity is the speed and direction of an object at the end of its motion or at a specific point in time. It is a key concept in the study of one-dimensional kinematics, which describes the motion of objects along a straight line.
Free Fall: Free fall is the motion of an object where gravity is the only force acting upon it, leading to uniform acceleration towards the center of a gravitational field. This concept is crucial for understanding how objects behave when they are dropped or thrown, as it allows for the application of motion equations to describe their motion under constant acceleration.
Initial position: Initial position refers to the starting point of an object in one-dimensional motion, represented by a specific location on a coordinate system. This term is crucial in kinematics as it sets the stage for analyzing how an object's position changes over time due to its motion. Understanding initial position helps in solving problems involving displacement, velocity, and acceleration by providing a reference point from which measurements are taken.
Initial velocity: Initial velocity refers to the starting speed and direction of an object in motion at the beginning of a time interval. It is a critical concept because it serves as the baseline for analyzing motion, influencing how an object's position, speed, and acceleration change over time. Understanding initial velocity helps in applying equations of motion to predict an object's future position and velocity as it moves along a path.
Instantaneous velocity: Instantaneous velocity is the velocity of an object at a specific moment in time. It is represented as the derivative of the position function with respect to time.
Instantaneous Velocity: Instantaneous velocity is the rate of change of an object's position at a specific instant in time. It represents the velocity of an object at a particular moment, as opposed to the average velocity over a period of time.
Kinematics: Kinematics is the branch of physics that studies the motion of objects without considering the forces that cause the motion. It focuses on parameters such as position, velocity, acceleration, and time, allowing us to describe how an object moves in space over time and understand various forms of motion.
Newton's Laws of Motion: Newton's Laws of Motion are a set of three fundamental principles that describe the relationship between an object and the forces acting upon it, governing the motion of objects and the interactions between them. These laws form the foundation of classical mechanics and are crucial in understanding various topics in introductory college physics.
Newton’s second law of motion: Newton’s second law of motion states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Mathematically, it is represented as $F = ma$, where $F$ is the net force, $m$ is the mass, and $a$ is the acceleration.
Point Particle: A point particle is an idealized object in physics that has mass but occupies no volume, meaning it can be treated as having no dimensions. This simplification allows for easier calculations and analysis in one-dimensional kinematics, as the complex shape and size of real objects can be disregarded to focus on their motion and forces acting on them.
Reference Frame: A reference frame is a coordinate system used to describe the position, motion, and other physical quantities of an object or event. It provides a frame of reference from which measurements and observations can be made. This term is crucial in understanding various topics in physics, including displacement, one-dimensional kinematics, graphical analysis of motion, and the concepts of simultaneity and time dilation.
Scalar: A scalar is a physical quantity that has only magnitude and no direction. Examples include mass, temperature, and electric potential.
Scalar: A scalar is a physical quantity that has only a magnitude, or numerical value, and no direction. Scalars are contrasted with vectors, which have both a magnitude and a direction. Scalars are commonly used in physics to describe various physical properties and quantities.
Second: The second is the base unit of time in the International System of Units (SI). It is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom. The second is a fundamental physical quantity that is essential for understanding and measuring various physical phenomena across multiple fields, including physics, chemistry, and engineering.
Trajectory: Trajectory is the path that a moving object follows through space as a function of time. It is determined by factors such as initial velocity, angle of launch, and the forces acting on the object (e.g., gravity).
Trajectory: A trajectory is the path or curve that an object follows through space over time. It describes the motion and position of an object as it moves from one point to another, taking into account factors such as initial position, velocity, acceleration, and the effects of forces acting on the object.
V0: v0 is the initial velocity of an object, which represents the speed and direction of the object at the starting point of its motion. It is a fundamental concept in the study of one-dimensional kinematics, as it is one of the key variables that determines the object's position and motion over time.
Velocity: Velocity is a vector quantity that describes the rate of change in the position of an object over time. It includes both the speed of the object and the direction of its motion. Velocity is a crucial concept in understanding the motion of objects and the fundamental principles of physics.
X-axis: The x-axis is a horizontal reference line that represents the horizontal or left-right dimension in a coordinate system. It is one of the primary axes used to describe the position and motion of objects in one-dimensional kinematics.
Δx: Δx, or delta x, represents the change in position or displacement of an object over a given time interval. It is a fundamental concept in the study of kinematics, which is the branch of physics that describes the motion of objects without considering the forces that cause the motion.
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