Final answer:
The horse can accelerate a buggy forward due to Newton's third law, where the force the horse's hooves exert backward on the ground causes an equal and opposite forward force, propelling the horse and buggy.
Step-by-step explanation:
Laura is observing an example of Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. When a horse pulls a buggy, the horse exerts a force on the ground in the backward direction. According to Newton's third law, the ground exerts an equal and opposite force on the horse in the forward direction. This reaction force is what actually propels the horse and the buggy forward, allowing them to accelerate. This can be confusing because the horse and buggy are connected, so it might seem like the forces they exert on each other could cancel out, but it is the force between the horse's hooves and the ground that's crucial for acceleration. Notably, for the horse and buggy system to accelerate, the friction between the horse's hooves and the ground must be greater than the total drag force, which includes the force of the buggy pulling back on the horse. It's also important to distinguish between scenarios involving Newton's first law (where net force is zero and the system is at a constant velocity) and Newton's second law (where net force is not zero, causing acceleration).