Final answer:
At 20 mph, the distance it takes for a car with lawful brakes to stop depends on various factors and would need more information for an accurate calculation.
Step-by-step explanation:
In order to determine the distance it takes for a car to stop at a certain speed, we need to consider the velocity, reaction time, and braking distance. The question states that we should not include thinking and reaction time, so we can focus on the braking distance.
At 20 mph, which is equivalent to 29.33 feet per second, the lawful brakes must stop a car within a certain distance. The specific distance would depend on various factors such as road conditions and the coefficient of friction between the tires and the road surface. We would need more information to calculate the exact distance.