Final answer:
Before collision, a car moving at constant velocity experiences balanced forces with a net force of zero. During collision with a wall, a large nonzero net force acts on the car, leading to rapid deceleration and an equal and opposite force exerted on the wall as per Newton's third law, demonstrating unbalanced forces and conservation of momentum.
Step-by-step explanation:
Forces Acting on a Moving Car Before and During Collision
Before the collision, as a car moves at constant velocity, according to Newton's first law, the net force acting on the car is zero. This means that the forward frictional force exerted by the road on the tires is exactly balanced by the drag force (air resistance) and any other opposing forces. The car does not accelerate, which tells us that the forces are in equilibrium.
During the collision with the wall, Newton’s laws dictate that there will be an instantaneous change in velocity, resulting in a nonzero net force applied to the car. This force is due to the wall exerting a force on the car equal in magnitude and opposite in direction to the car's momentum. According to Newton's third law, the car exerts an equal and opposite force on the wall. The car decelerates rapidly, indicating that the forces during the collision are unbalanced.
When considering the momentum of the car, it is important to note that momentum is conserved in a collision. In the case of the car and the wall, the car's momentum changes, but the wall's large mass combined with its anchoring makes its momentum change negligible, effectively making the wall a fixed object.