Question

an elevaror desxends into a mine shaft at the rate od -13m/min.if the descend starts from 20m above the ground level,how long will it take to reach-240m​

Answer 1

✬ Time = 86.67 minutes ✬

Step-by-step explanation:

Given:

• Elevator descends into mine craft at speed 3 m/min.
• It starts descending from 20 m above the ground.

To Find:

• How much time will it take to reach –240 m?

Solution: Let the distance above mine craft be (+ve) and and below be (–ve)

As we know that

★ Speed = Distance/Time ★

[ In first condition when it starts descending from 15 m above ]

$\implies{\rm }$ 3 = 20/t¹

$\implies{\rm }$ 3t¹ = 20

$\implies{\rm }$ t¹ = 20/3 = 6.67 mins

So, Elevator took 6.67 minutes to reach the ground level.

[ In second condition when it starts descending from ground level –240 m ]

$\implies{\rm }$ 3 = 240/t²

$\implies{\rm }$ 3t² = 240

$\implies{\rm }$ t² = 240/3 = 80 mins

So,

➨ Total time taken = t¹ + t²

➨ 80 + 6.67 = 86.67 minutes

Hence, elevator will take 86.67 minutes to reach –240 m or 240 below the ground.