Falling Objects: Free Fall

Vocabulary flashcards covering key concepts from the Falling Objects: Free Fall lecture notes.

Free fall

Motion in which gravity is the only force acting on an object, and the object moves only vertically (up or down).

Gravity

The force of attraction that pulls objects toward Earth’s center, causing vertical acceleration.

Acceleration due to gravity (g)

The constant downward acceleration near Earth’s surface, about 9.8 m/s^2 (g ≈ 9.8 m/s^2).

Velocity in free fall

The rate of change of position; in constant g, velocity increases with time and is given by v = g t.

Distance fallen in free fall

Vertical distance traveled under constant acceleration: d = 1/2 g t^2.

Air resistance (drag)

A force from the air that opposes motion, slowing falling objects; depends on mass, surface area, and shape.

Vacuum

A space with no air; in vacuum, all bodies fall with the same acceleration regardless of mass.

Weight

The gravitational force on an object, W = m g, measured in newtons (N).

Gravitational constant (G)

The universal constant in Newton’s law of gravitation: G ≈ 6.674×10^-11 m^3 kg^-1 s^-2.

Mass of Earth

The total amount of matter in Earth, approximately 5.972 × 10^24 kg.

Distance Earth–Moon

Average center-to-center distance about 3.84 × 10^8 meters.

Acceleration on Moon due to Earth’s gravity

The downward acceleration at lunar distance due to Earth's gravity, about 0.003 m/s^2.

Weightlessness

A state where apparent weight is zero, such as during free fall or certain flight maneuvers.

Parabolic flight

A flight path that creates short periods of weightlessness by following a parabola.

G-Force One

A powered aircraft used to produce weightless conditions during parabolic flight.

Apex (top of trajectory)

The highest point of a projectile’s path where vertical velocity is momentarily zero, while gravity continues to act.

Throwing upward (projectile motion)

If a ball is thrown upward, gravity acts downward throughout, eventually reversing the motion as velocity changes sign.

Acceleration remains downward

Even at the top of the path, gravitational acceleration is constant downward; velocity changes.

Independence of mass in vacuum

In a vacuum, all objects accelerate at the same rate under gravity, regardless of mass.

Surface gravity on planets

Gravity experienced on a planet’s surface; varies with a planet’s mass and radius.

Kinematic relations in free fall

Under constant gravity, velocity and distance relate as v = g t and d = 1/2 g t^2.

Feather vs brick in air vs vacuum

In air, air resistance makes a feather fall slower; in vacuum, both fall at the same rate due to identical g.

Newton’s law of gravitation

F = G m1 m2 / r^2; gravitational force between two masses.