Do heavier objects really fall faster?

In a vacuum, no. Without air resistance, the acceleration of an object depends only on the strength of the gravitational field (g). A feather and a hammer fall at the same rate on the Moon. On Earth, heavier objects often *seem* to fall faster because they have a higher mass-to-cross-sectional-area ratio, making the effect of air resistance less significant compared to their weight.

What is terminal velocity, and what determines it?

Terminal velocity is the constant maximum speed an object reaches when the upward force of air resistance balances the downward force of gravity, resulting in zero net force and zero acceleration. It depends on the object's mass, cross-sectional area, shape (drag coefficient), and the density of the fluid (like air) it's falling through.

Why does the simulator use a simplified model for air resistance?

Real-world air resistance is complex, depending on an object's shape, surface texture, and the turbulence of the airflow. A simplified model using a drag coefficient allows us to capture the essential behavior—deceleration and terminal velocity—without overwhelming computational complexity, making the core physics principle clear for learners.

Is an object in free fall weightless?

An object in free fall experiences apparent weightlessness because it and its surroundings are accelerating downward at the same rate. However, it still has mass and is still acted upon by the gravitational force (its weight). This is the same sensation astronauts feel in orbit, which is continuous free fall around the Earth.

Free Fall

Free fall is the motion of an object solely under the influence of gravity, a foundational concept in classical mechanics. This simulator visualizes this motion for one or two objects dropped from the same height. It demonstrates the core principle, first established by Galileo, that in a vacuum (where air resistance is negligible), all objects fall with the same constant acceleration regardless of their mass. This acceleration due to gravity near Earth's surface, denoted as *g*, is approximately 9.8 m/s². The kinematic equations govern the motion: velocity as a function of time is v = g*t, and the distance fallen is d = (1/2)gt². A key feature of this model is the option to introduce a simplified form of air resistance, often modeled as a force proportional to the object's speed or the square of its speed. This resistive force opposes gravity, causing the object to reach a terminal velocity where the net force is zero and acceleration ceases. The simulator makes several simplifications: it treats *g* as constant, assumes a uniform gravitational field, and models air resistance with a simplified drag coefficient. It does not account for factors like buoyancy, variation in *g* with altitude, or complex aerodynamic shapes. By interacting with this tool, students can directly test Galileo's famous thought experiment, observe how mass and cross-sectional area influence motion with air resistance, and gain intuition for the relationships between displacement, velocity, acceleration, and time in uniformly accelerated motion.

Who it's for: High school and introductory college physics students studying kinematics, Newton's laws of motion, and the effects of drag forces.

Key terms

Free Fall
Acceleration due to Gravity (g)
Kinematic Equations
Air Resistance (Drag)
Terminal Velocity
Galileo's Law of Falling Bodies
Newton's Second Law
Projectile Motion

Live graphs

How it works

In vacuum, all objects fall with the same acceleration g regardless of mass — Galileo’s famous result. With linear air resistance, acceleration decreases as speed grows until terminal velocity is approached. Without drag, each timestep uses exact constant-g kinematics (no Euler drift in y, v). With drag, motion is integrated numerically. Height is above ground with downward-positive velocity.

Key equations

No drag:y = h − ½gt², v = gt

With linear drag (model):a = g − (k/m)v

Frequently asked questions

Do heavier objects really fall faster?: In a vacuum, no. Without air resistance, the acceleration of an object depends only on the strength of the gravitational field (g). A feather and a hammer fall at the same rate on the Moon. On Earth, heavier objects often *seem* to fall faster because they have a higher mass-to-cross-sectional-area ratio, making the effect of air resistance less significant compared to their weight.
What is terminal velocity, and what determines it?: Terminal velocity is the constant maximum speed an object reaches when the upward force of air resistance balances the downward force of gravity, resulting in zero net force and zero acceleration. It depends on the object's mass, cross-sectional area, shape (drag coefficient), and the density of the fluid (like air) it's falling through.
Why does the simulator use a simplified model for air resistance?: Real-world air resistance is complex, depending on an object's shape, surface texture, and the turbulence of the airflow. A simplified model using a drag coefficient allows us to capture the essential behavior—deceleration and terminal velocity—without overwhelming computational complexity, making the core physics principle clear for learners.
Is an object in free fall weightless?: An object in free fall experiences apparent weightlessness because it and its surroundings are accelerating downward at the same rate. However, it still has mass and is still acted upon by the gravitational force (its weight). This is the same sensation astronauts feel in orbit, which is continuous free fall around the Earth.

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