How do the forces required to stop each dummy compare?

Question

Two safety dummies (of equal mass) are being used to test seat belts. Dummy A has a wide seat belt, and Dummy B has a narrow seat belt. Both dummies are crashed into a barrier while in the same car. How do the forces required to stop each dummy compare? is what the question is asking.

 

However, I know that the forces on the two dummies would be equal. But why? Could you please explain this concept using physics terms? I would highly appreciate it.

Answer 1

First of all, congratulations on intuitively knowing that the forces on the two dummies would be equal. To answer your question of why, let's review what force actually is. 

 

Force = mass X acceleration

 

The question states that the dummies are of equal mass, therefore the only other variable that would make the forces differ is acceleration. So the question is do both dummies experience the same acceleration?