Question

An elevator descends into a mine shaft at rate of 15 metre per minute. a) What will be its position after 1 hour? b) If it begins to descend 25m above ground, what will be its position after 45 minutes?

Answer 1

To find out the position of the elevator after a certain time, we need to use the rate of descent and the amount of time it has been descending.

a) The rate of descent is 15 meters per minute. After 1 hour, or 60 minutes, the elevator has descended 15 meters per minute times 60 minutes, which equals 900 meters. The position of the elevator is therefore 900 meters below the starting point, or -900 meters, considering the start point as zero.
b) If the elevator begins its descent 25 meters above ground, that means its initial position is +25 meters relative to the ground. Now, let's find out how much it descends after 45 minutes. We multiply the descent rate (15 meters per minute) by the amount of time sinking (45 minutes), and the result is 675 meters. To find out the final position of the elevator, we need to subtract the distance descended from the initial position: 25 meters - 675 meters = -650 meters. The negative sign indicates that the elevator is below ground.
So, after 1 hour, the elevator is 900 meters below the starting point, and when it starts 25 meters above ground and operates for 45 minutes, it ends up 650 meters below ground.