Final answer:
The most important factor in determining how hard a vehicle hits a fixed object is the change in momentum, which is determined by the vehicle's mass and velocity before the collision. Other factors, such as the duration of the collision and the ability of the vehicle to absorb the impact, can also affect the force exerted on the vehicle.
Step-by-step explanation:
The most important factor in determining how hard a vehicle hits a fixed object is the change in momentum. The change in momentum of a vehicle is determined by its mass and velocity before the collision.
When a vehicle collides with a fixed object, such as a wall, the force exerted on the vehicle depends on the change in momentum. The greater the change in momentum, the greater the force exerted by the object on the vehicle. This can be seen in the equation:
Force = Change in momentum / Time
Other factors, such as the duration of the collision and the ability of the vehicle to crumple or absorb the impact, can also affect the force exerted on the vehicle.