Final answer:
The cycle time for a single-engine scraper can be determined by considering the time it takes to travel from the pit to the fill and back. First, calculate the time to haul one way using the average haul speed and distance. Next, calculate the time to return by considering the average return speed and the time required to accelerate and decelerate. Finally, add the haul time and return time to determine the cycle time.
Step-by-step explanation:
The cycle time for a single-engine scraper can be determined by considering the time it takes for the scraper to travel from the pit to the fill and back. First, we need to calculate the time it takes to travel one way. The distance from the pit to the fill is 900 ft, and the average haul speed is 14 mph. We convert the distance to miles by dividing by 5280, and then calculate the time using the formula: time = distance / speed. So, the time to haul one way is (900 ft / 5280 ft/mi) / (14 mph), which is approximately 0.09 hours.
Next, we calculate the time it takes to return to the pit. The average return speed is 20 mph, but we need to account for the time required to accelerate and decelerate. At an average speed of 5 mph, it takes 200 ft to accelerate and decelerate. So, the total distance to be traveled for the return trip is 900 ft + 200 ft + 200 ft = 1300 ft. Using the formula time = distance / speed, the time to return is (1300 ft / 5280 ft/mi) / (20 mph), which is approximately 0.04 hours.
Finally, we calculate the cycle time by adding the time to haul one way and the time to return: 0.09 hours + 0.04 hours = 0.13 hours. Therefore, the cycle time for the single-engine scraper is 0.13 hours or 7.8 minutes.