It sounds as though you are asking about these scenarios:
1) two of the smallest hatchback cars collide
v.
2) two of the largest pickup trucks collide
??
If you are wondering about comparing these collisions at the same SPEEDS...then there are some things we can say.
With
A) the small cars both of the same make & model year and equipped identically to each other, and
the large trucks both of the same make & model year and equipped identically to each other,
AND
B) a collision type which would look the same from each vehicle's perspective (i.e., a head-on collision, squarely hit)
AND
C) at the SAME speed for EVERY vehicle,
then
we expect both sets of passengers in the same group (small car or big truck) to sustain substantially similar injuries, etc., by the symmetry of the set-up.
However, crashes are mostly about the behavior of the vehicles under inelastic collisions (where the energy of motion is NOT conserved)--so that much of the energy of motion has to be absorbed by the vehicles (this is why vehicles are now designed with "crumple zones", areas designed to absorb energy via being deformed).
The real question is what is the relative energy to be dissipated in the two crashes.
Since we are assuming straight-line travel,
E_j = m__j * (v_j^2)/2
where
E_j is the kinetic energy of the jth vehicle,
m_j is its mass, and
v_j is its speed.
For your given problem, I'll wager that
m_{smallest hatchback} < m_{large pickup truck}
For a 2024 Mitsubishi Mirage ES CVT, the weight (not mass) is
2084#
The 2005 International CXT, the largest standard production pickup ever made, has a weight of
14,500#
So the ratio of the energies of the a SINGLE CXT to a SINGLE Mirage is
r ≡ E_{CXT}/E_{Mirage} = m_{CXT}/m_{Mirage} = w_{CXT}/w_{Mirage} (ratio of weights)
or
r = (14,500 / 2084)
for 6.96 x the energy!
It also has lot more mass, but I'd rather take my chances with the vehicle having the LOWER mass and LESS energy to have to absorb.
