Final answer:
Due to Newton's first law of inertia, the cupcakes continued moving forward when the woman's car stopped abruptly, causing them to smash into the dashboard. The woman was restrained by her seatbelt, which applied a backward unbalanced force, preventing her from moving forward like the cupcakes.
Step-by-step explanation:
When the woman applied her brakes suddenly, the car stopped due to the force exerted by the brakes. However, the cupcakes, which were an open box sitting inside the car, were in motion with the same velocity as the car before the brakes were applied. According to Newton's first law of inertia, an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. In this situation, there was no force directly applied to the cupcakes to cause them to stop with the car. As a result, inertia caused the cupcakes to keep moving forward even though the car had stopped, resulting in them flying into the dashboard and becoming 'smushcakes.'
The seatbelt constrained the woman by applying a backward force, which prevented her from moving forward like the cupcakes. This is an application of Newton's second law, where the acceleration of an object is the result of an unbalanced force acting on it, and is inversely proportional to the mass of the object. In this case, the seatbelt acted as the unbalanced force that changed the woman's state of motion to match that of the stopping car.