Final answer:
The impact of a car crashing into a wall is that the velocity decreases.
Step-by-step explanation:
When an automobile crashes into a wall, there is a change in the car's velocity. In this case, since the car is moving at 4 ft/s before the collision, the impact will cause the velocity to decrease. Therefore, the answer is a. Velocity decreases.
When an automobile weighing 3000 lb and moving at 4 ft/s crashes into a wall in 0.06 seconds, the impact results in force increasing due to the abrupt deceleration of the car. According to Newton's second law of motion (Force = mass × acceleration), the force can be calculated by determining the rate of change of velocity over the time interval of the collision. Given that the velocity decreases to zero in a very short time, the force exerted on the automobile by the wall is significant.
In similar scenarios, such as the provided example where a car with a mass of 2500 kg hits a wall and experiences an average force of 740,000 N over a 0.22-second interval, we can calculate the initial speed prior to the collision using the impulse-momentum theorem. The impulse exerted on the car is equal to the change in momentum, which can be used to determine the car's initial velocity before impact.