Final answer:
The minimum speed at which the conveyor must move is approximately 7.08 feet per second.
Step-by-step explanation:
To calculate the minimum speed that the conveyor must move, we need to determine the maximum time it takes for the casting to cool by 7°F. Since the cooling rate of the casting is 0.3°F per second, we divide 7°F by 0.3°F/second to find the maximum time in seconds:
t = 7°F / 0.3°F/second = 23.33 seconds.
Since the distance is given in yards, we need to convert it to feet: 1 yard = 3 feet. So, the distance is 55 yards x 3 feet/yard = 165 feet.
The minimum speed of the conveyor can be calculated by dividing the distance by the maximum time:
speed = distance/time = 165 feet / 23.33 seconds ≈ 7.08 feet per second.