Answer:
a) no vehicle has a larger magnitude force acting on it.
b) The vehicle's acceleration that has the larger magnitude will be the lighter one, the small car.
Step-by-step explanation:
If we assume that during the collision there are no external forces acting on both vehicles (due to the very short collision time), the only forces acting are those due to Newton's 3rd Law, which by definition, are equal and opposite each other, one due to the car on the 18wheeler, and the other caused by the 18wheeler to the car.
So, as both forces are equal and no vehicle has a larger magnitude force acting on it.
Now, applying 2nd Newton's Law to each vehicle, it must be true the following:
F₁₂ = F₂₁ ∴ m₁a₁ = m₂a₂.
where m₁ = car mass m₂= 18wheeler mass.
As m₁ is much much smaller than m₂, it follows that a₁ will be greater than a₂.