When a vehicle hits a fixed object like a tree, what factor most determines the impact severity?

• A. The color of the vehicle
• B. The weather
• C. The speed of the vehicle
• D. The age of the driver

Answer: (C)

When a vehicle hits a fixed object, the main factor driving how severe the impact is the speed at which you’re traveling at the moment of impact. The crash energy that must be absorbed by the car and its occupants equals the vehicle’s kinetic energy, which grows with the square of speed (energy = 1/2 mv^2). So, even a small increase in speed can dramatically increase the energy that has to be dissipated, leading to stronger deceleration forces and more potential for injury. Safety systems like crumple zones, seat belts, and airbags help by spreading that deceleration over a longer time, reducing peak forces, but they can’t change the fact that higher impact speed means a harsher crash. Weather or road conditions can influence how you might collide, and driving age or the vehicle’s color don’t determine the crash’s physics, so they don’t set the severity.