Physics of Free Fall
Free fall is motion under gravity alone, with no air resistance or other forces. All objects free fall with the same acceleration regardless of mass-a principle Galileo demonstrated. The equations are: v = gt (velocity), h = (1/2)gt^2 (distance), and v^2 = 2gh (velocity-distance). On Earth, g = 9.81 m/s^2. After 1 second, velocity is 9.81 m/s; after 2 seconds, 19.62 m/s. Distance fallen increases with time squared.
Real vs Ideal Free Fall
True free fall only occurs in vacuum. In air, resistance affects motion, eventually causing terminal velocity where drag force equals weight. Skydivers reach terminal velocity around 53 m/s (190 km/h) in spread position or 90 m/s (320 km/h) head-down. Light objects like feathers quickly reach low terminal velocities. Astronauts in orbit experience continuous free fall-they're falling around Earth. Understanding the difference between idealized and real free fall is crucial for safety and engineering applications.
Applications and Examples
Free fall calculations help determine safe heights, design safety equipment, and analyze accidents. Engineers use free fall principles to design elevators, amusement park rides, and shock absorbers. The formula helps calculate impact velocities in falling object hazards. Skydivers and BASE jumpers must understand free fall to deploy parachutes safely. Smartphone accelerometers detect free fall to protect hard drives. Even simple tasks like estimating the depth of a well by timing a stone's fall use these principles.
Quick Tips
- Always verify units are consistent
- Use scientific notation for very large/small numbers
- Results are approximations — real conditions may vary
Frequently Asked Questions
In vacuum, yes-all objects accelerate at g regardless of mass. Galileo demonstrated this. On Earth, air resistance affects lighter objects more, so in practice, heavy objects often fall faster.
Terminal velocity is the constant speed reached when air resistance force equals gravitational force, so net force is zero and acceleration stops. For humans, it's about 53 m/s (190 km/h) in spread position.
Ignoring air resistance, velocity after 10 seconds is v = gt = 9.81 x 10 = 98.1 m/s (353 km/h or 219 mph). In reality, most people would approach terminal velocity before 10 seconds.
Distance fallen in the first second is h = (1/2)gt^2 = (1/2) x 9.81 x 1^2 = 4.9 meters (about 16 feet). Distance increases quadratically, so the second second covers 14.7m more.
Astronauts are in continuous free fall around Earth. They fall toward Earth but also move forward fast enough that they keep missing it, creating an orbit. This creates apparent weightlessness.