Final answer:
The stopping distance for a car varies with speed and road conditions. On dry concrete, the stopping distance at 30 mph is approximately 83.63 feet, and at 50 mph, it's approximately 235.20 feet; these distances increase on wet concrete and also with driver reaction time.
Step-by-step explanation:
To determine how many feet it takes for a car to come to a complete stop when driving at 30 miles per hour (mph) and 50 mph, we need to consider the physics of deceleration and factors such as road condition and reaction time. For this explanation, let's assume that we have dry concrete with a deceleration rate of 7.00 m/s² and also consider wet concrete with a deceleration rate of 5.00 m/s².
Firstly, let's convert the speeds from mph to meters per second (m/s). 30 mph is approximately 13.4 m/s, and 50 mph is about 22.4 m/s. We use the formula for stopping distance: distance = (speed)^2 / (2 * deceleration rate). On dry concrete, the stopping distance for a car moving at 13.4 m/s (30 mph) is 25.48 meters (83.63 feet), and at 22.4 m/s (50 mph) it is 71.68 meters (235.20 feet). On wet concrete, the distances are longer due to the reduced deceleration rate.
If we take into account a reaction time of 0.5 seconds before beginning to brake, the driver will travel an additional distance during that time. For example, at 30 mph, they will travel another 6.7 meters (22 feet approx.) just reacting, thus increasing the total stopping distance.
In conclusion, the stopping distance varies with speed and conditions, and it's vital for drivers to be aware of these variables to drive safely.