text: how do you find the force on a persons body when in a car accident into another car?   use newton's second law of motion. f=ma. force on an object(the car) is equal to the mass(weight)of the car times the acceleration(or in the case of an accident the deceleration). it's harder to determine the force on a passenger because the seatbelt is designed to minimize the impact of an accident. airbags do too!