Car Crash Calculator
Calculate impact forces, g-forces, and collision physics in vehicle crashes
Calculate Car Crash Impact Force
Average adult mass is 70 kg
Speed just before impact
Safety Features
Impact Force Results
Formula used: F = mv²/(2d)
Speed: 8.3 m/s
Stopping distance: 4.0 cm
Safety factor: No seat belt - extreme danger
Peak deceleration: 868 m/s²
Safety Analysis
Example Calculation
70 kg Driver at 30 km/h Without Seatbelt
Initial speed: 30 km/h = 8.33 m/s
Stopping distance: 4 cm (hits windshield/steering wheel)
Kinetic energy: ½mv² = ½ × 70 × 8.33² = 2,430 J
Impact Calculation
F = mv²/(2d) = 70 × 8.33²/(2 × 0.04)
F = 70 × 69.39/0.08
F = 60,590 N = 60.6 kN
G-force = 60,590/(70 × 9.81) = 88.3g
Equivalent weight = 6.2 tonnes pressing on chest!
With Seatbelt (20 cm stopping distance)
F = 70 × 8.33²/(2 × 0.20) = 12,118 N = 12.1 kN
G-force = 17.7g (80% reduction!)
Equivalent weight = 1.2 tonnes
Physics Principles
Impact Force
F = mv²/(2d)
Work-energy theorem
Stopping Time
t = mv/F
Impulse-momentum theorem
G-Force
g = F/(m × 9.81)
Acceleration relative to gravity
Crash Safety Facts
Seat belts reduce death rates by 45%
Airbags provide additional 20cm stopping distance
Most crash injuries occur in first 10-20 milliseconds
Crumple zones increase stopping distance by 50-100cm
Forces above 60g for >3ms can be fatal (NHTSA)
Understanding Car Crash Physics
What Happens During a Crash?
In a car crash, the vehicle stops almost instantly, but occupants continue moving at the original speed due to inertia. The impact force depends on how quickly they decelerate - the shorter the stopping distance, the greater the force.
Why Distance Matters
- •Without seatbelt: Body hits steering wheel/windshield (4cm stopping distance)
- •With seatbelt: Body stretches seatbelt material (20cm stopping distance)
- •5× longer distance = 5× less force (inverse relationship)
The Physics Behind Impact
F = mv²/(2d)
Work-Energy Theorem
- F: Average impact force (Newtons)
- m: Mass of person/object (kg)
- v: Initial velocity before crash (m/s)
- d: Stopping distance during collision (m)
Key Insight: Force increases with the square of velocity - doubling speed means 4× more force, not 2×!