North Carolina RADAR State Practice Exam

What is the braking distance at a speed of 40 MPH?

1. 44 ft

2. 81 ft

3. 66 ft

4. 100 ft

The correct answer is: 81 ft

To calculate the braking distance at a speed of 40 MPH, one must consider both the physics of braking and the conditions affecting stopping distance, such as perception time, reaction time, and the coefficients of friction for various surfaces. At 40 MPH, the typical rule of thumb for stopping distance – which includes both the reaction distance and the braking distance – is approximately 4 times the square of the speed in miles per hour. Therefore: 1. The square of 40 is 1600. 2. Taking into account that the stopping distance uses a multiplier of 1.5 for reality checks, the theoretical braking distance is closer to the option of 81 feet when calculated under ideal conditions without external factors affecting it. Each vehicle, as well as road conditions (wet, dry, debris), can further customize this figure, which can result in a practical braking distance of around 81 feet, especially considering common variables drivers face like tire grip and the surface of the roads. Hence, this makes the option of 81 feet the most reasonable answer to the question regarding braking distance at a speed of 40 MPH.