Answer :
Final answer:
To calculate the time it takes for an elevator descending at 7 m per minute to reach -480 meters from 10 meters above ground, total distance traveled is -490 meters. Dividing this by the speed gives a time of 70 minutes, which is option B.
Explanation:
The question involves calculating the time it takes for an elevator to descend into a mine shaft given a constant speed and starting position above ground level. Since the elevator descends at a rate of 7 m per minute, we need to find out how many minutes it would take to reach -480 meters from a starting point of 10 meters above ground level.
The total distance the elevator needs to travel is the difference between its final position and its starting position:
Total distance to descend = Final position - Starting position
Total distance to descend = -480 m - 10 m = -490 m
Since the distance is negative, it indicates that the elevator is moving downward. We divide the total distance by the speed of the elevator to find the time:
Time = Total distance / Speed
Time = -490 m / -7 m/min = 70 minutes
Therefore, it would take 70 minutes for the elevator to reach -480 meters, which corresponds to answer choice B.
