During collisions, more massive vehicles provide greater safety than smaller ones. How to explain this on the basis of conservation of momentum?
1 Answer
During crash many attributes of colliding cars come into play. These are inertia, the relationship between crash forces and inertia, momentum and impulse.
As such it is difficult to explain safety of cars and its passengers on the basis of Law of conservation of momentum alone.
We can certainly argue that in case two cars move at the same speed towards each-other and are involved in a head-on collision, the outcome of crash depends partly on the cars’ relative weights.
The heavier of the two cars is likely to push the lighter car backward during the impact. This implies that the change of velocity of the heavier car will be much less than the change of velocity of the lighter car.
We know that during a car crash major factor that causes injury to the occupants is the fact that the car stops suddenly, but the occupants continue to move due to inertia. This causes a sudden and violent impact between the occupants and the interior of the car.
As explained above, the greater momentum of the larger car helps in moving it with a smaller change in velocity at the time of crash. As the car's velocity change to a lesser extent, the occupants collide with the interior of the car with lower relative velocity. This reduces or eliminates the chances of injuries to them.
