The force of impact of a collision is affected by vehicle's aceable

By vehicle's  __kinetic energy__.

Explanation:

The concept of Kinetic energy is: the more energy of motion their vehicle has (speed) the greater will be the force of the impact. Also weight of the vehicle and its occupants represent a factor in a collision, for example; larger and heavier vehicles tend to have greater the energy and momentum and consequently bigger force of impact.

there are no options provided but you can choose among the following gender-neutral pronouns: zir, hir, eir, vis, tem, eir.

in the normal course of maintaining a pronoun-antecedent agreement, we could have used the words his or her but since we are also required to use gender-neutral language, we need to replace it with its equivalent gender-neutral pronoun.