The force at impact is the primary factor associated with fatalities.

• A. Mass
• B. Velocity
• C. Force
• D. Friction

Answer: (C)

The main idea is that injuries from a crash come from the force the body experiences as it is rapidly brought to a stop. When the vehicle hits and the occupant must slow from their current speed to zero in a very short time, large deceleration occurs. That rapid deceleration creates high forces on the body (force = mass × acceleration). The bigger the deceleration or the greater the mass involved, the larger the impact force, and the higher the risk of fatal injury. Friction isn’t the primary driver of fatal injuries in most crashes, and while faster speed increases the potential deceleration, it’s the resulting impact force that directly drives the danger to life. Safety devices like seat belts and airbags reduce peak forces by spreading deceleration over a longer time and distance, which is why they lower fatality risk.