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Free Fall Impact Calculator

Calculate terminal velocity, kinetic energy, and impact force for falling bodies with air resistance. Ideal for physics students and safety analysis.

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About

Understanding the physics of a fall requires more than just gravity. It demands an appreciation for the atmosphere and the brutal reality of deceleration. This tool computes the final velocity of a falling object by accounting for air resistance (drag), which significantly alters the outcome compared to a vacuum-only calculation. It also estimates the impact force, a critical variable that depends heavily on how quickly the object stops upon hitting the ground.

Accuracy in these calculations is vital for forensic engineering, extreme sports safety planning, and physics education. A miscalculation in drag coefficient or stopping distance can lead to vastly different energy estimates. This calculator helps visualize the difference between a controlled descent and a catastrophic failure, translating abstract kinetic energy figures into relatable crash scenarios.

impact force terminal velocity kinetic energy physics calculator free fall

Formulas

The calculation uses the standard drag equation to determine terminal velocity and the dynamic motion equation for velocity at impact.

Terminal Velocity:

vt = āˆš2mgĻACd

Velocity at Height h:

v = vt āˆš1 āˆ’ expāˆ’ĻACdhm

Average Impact Force:

Favg = 0.5 m v2dstop

Where m is mass, g is gravity (9.81 m/s2), Ļ is air density (1.225 kg/m3), A is cross-sectional area, Cd is the drag coefficient, and dstop is the distance over which the object decelerates upon impact.

Reference Data

ScenarioDrag Coefficient (Cd)Typical Surface Area (m2)Terminal Velocity (approx)
Skydiver (Belly-to-Earth)1.00.754 m/s (120 mph)
Skydiver (Head-Down)0.70.1889 m/s (200 mph)
Human (Curled/Tuck)1.20.560 m/s (134 mph)
Sphere (Smooth)0.47VariableDepends on Mass/Radius
Cube (Flat Face)1.05VariableLower than sphere
Streamlined Body0.04VariableVery High
Parachute (Deployed)1.7525+5 m/s (11 mph)
Falling Brick2.10.02High acceleration

Frequently Asked Questions

The stopping distance determines the acceleration (or deceleration) experienced. Stopping in 1 meter (like a safety net) versus 0.01 meters (concrete) results in a force 100 times greater for the same energy. This is why airbags work; they increase the distance and time over which you stop.
In a vacuum, objects accelerate indefinitely until impact. In the atmosphere, air resistance opposes motion. As speed increases, drag increases until it equals gravity. At this point, the object stops accelerating and reaches "Terminal Velocity".
This is a standard average at sea level. However, gravity fluctuates slightly depending on altitude and latitude. For most engineering and safety calculations involving falls under 10km, 9.81 is sufficiently accurate.
Kinetic energy is the energy an object possesses due to its motion. Impact force is the intensity of the blow when that energy is transferred to another object. High energy does not always mean high force if the stop is gradual.