Free Fall and Falling Objects Study Pack

Kibin's free study pack on Free Fall and Falling Objects includes a 3-section study guide, 8 quiz questions, 10 flashcards, and 1 open-ended Explain review question. Sign up free to track your progress toward mastery, plus upload your own notes and recordings to create personalized study packs organized by course.

Last updated May 21, 2026

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Free Fall and Falling Objects Study Guide

Master the physics of objects in free fall by working through gravitational acceleration, vertical kinematics, and the role of g = 9.80 m/s². This pack covers upward-thrown objects, peak-velocity behavior, and the three core equations linking displacement, velocity, and time — plus why mass never affects free-fall acceleration in an idealized, air-resistance-free model.

Key Takeaways

  • •Free fall is motion under the sole influence of gravity, with all objects experiencing the same downward acceleration of 9.80 m/s² near Earth's surface regardless of mass.
  • •The kinematic equations for constant acceleration apply directly to free fall, with the acceleration variable replaced by g = 9.80 m/s² directed downward.
  • •An object thrown upward still experiences the downward gravitational acceleration throughout its flight, causing it to decelerate on the way up, momentarily reach zero velocity at its peak, and accelerate back downward.
  • •At the peak of a vertical trajectory, instantaneous velocity equals zero but acceleration remains −9.80 m/s², meaning the object is still changing its velocity at that instant.
  • •Displacement, velocity, and time in free-fall problems are related through three key equations: v = v₀ + at, Δy = v₀t + ½at², and v² = v₀² + 2aΔy.
  • •Air resistance is neglected in the idealized free-fall model; in reality, drag forces reduce acceleration and produce a terminal velocity for falling objects.

What Free Fall Means and Why Mass Doesn't Matter

Free fall describes a specific physical situation — motion in which gravity is the only force acting on an object — and one of its most counterintuitive consequences is that every object falls at the same rate.

Defining Free Fall

  • •An object is in free fall when gravity is the only force influencing its motion; this requires ignoring air resistance.
  • •The term applies both to objects dropped from rest and to objects thrown upward or at an angle, as long as no other force acts on them after release.

Mass Independence of Gravitational Acceleration

  • •Near Earth's surface, every freely falling object accelerates downward at g = 9.80 m/s², regardless of whether it is a feather or a bowling ball.
  • •Galileo demonstrated this principle by showing that heavier objects do not fall faster; the confusion arises in everyday life because air resistance affects light or large-surface objects more than dense ones.
  • •The value g = 9.80 m/s² is an average for Earth's surface; it varies slightly with altitude and latitude but is treated as constant in introductory problems.

Direction Convention in Free-Fall Problems

  • •Physicists choose a positive direction before solving; the most common convention sets upward as positive, making g = −9.80 m/s².
  • •Some problems set downward as positive, in which case g = +9.80 m/s²; consistency within a single problem is what matters, not which convention is chosen.

Kinematic Equations Applied to Vertical Motion

The same three kinematic equations used for any constant-acceleration motion apply to free fall, with gravitational acceleration substituted for the general acceleration variable.

The Three Kinematic Equations for Free Fall

  • •v = v₀ + gt relates final velocity to initial velocity after time t under gravitational acceleration g.
  • •Δy = v₀t + ½gt² gives the vertical displacement when initial velocity and elapsed time are known.
  • •v² = v₀² + 2gΔy is useful when time is unknown and the relationship between velocity and position is needed directly.

Identifying Known and Unknown Variables

  • •Every free-fall problem involves five quantities: initial velocity (v₀), final velocity (v), gravitational acceleration (g), time (t), and displacement (Δy).
  • •With any three of these quantities known, the other two can be calculated using the equations above.
  • •g is always known (9.80 m/s² downward), so in practice you need only two additional known quantities to solve a problem completely.

Sign Discipline in Calculations

  • •Displacement Δy is positive when the object moves in the chosen positive direction and negative when it moves opposite to it.
  • •Failing to apply consistent signs is the most common source of arithmetic errors in free-fall problems; checking the physical reasonableness of answers helps catch sign mistakes.

About this Study Pack

Created by Kibin to help students review key concepts, prepare for exams, and study more effectively. This Study Pack was checked for accuracy and curriculum alignment using authoritative educational sources. See sources below.

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