Question

An elevator descends into a mine shaft at the rate of 7m/min. If the descent starts from 10m
above the ground level, how long will it take to reach - 480m. With steps

Answer 1

$\blue{\bold{\underline{\underline{Answer:}}}}$

$\green{\tt{\therefore{Time=70\:min}}}$

$\orange{\bold{\underline{\underline{Step-by-step\:explanation:}}}}$

$\green{\underline \bold{Given : }} \\ \tt: \implies Initial \: speed = 7 \: m/min \\ \\ \tt: \implies Total \: distance = 490 \: m \\ \\ \red{\underline \bold{To \: Find : }}\\ \tt: \implies Time \: taken = ?$

• According to given question :

$\tt \circ \: Acceleration = 0 \: {ms}^{2} \\ \\ \bold{As \: we \: know \: that} \\ \tt: \implies s = ut + \frac{1}{2} a {t}^{2} \\ \\ \tt: \implies 490 = 7 \times t + \frac{1}{2} \times 0 \times {t}^{2} \\ \\ \tt: \implies 490 = 7 \times t \\ \\ \tt: \implies t = \frac{490}{7} \\ \\ \green{\tt: \implies t = 70 \: min} \\ \\ \bold{Alternate \: method : } \\ \tt: \implies Time = \frac{Distance}{Speed} \\ \\ \tt: \implies Time = \frac{490}{7} \times \frac{metre \times min}{metre} \\ \\ \green{\tt: \implies Time = 70 \: min}$

Answer 2

Answer:

The time taken by the elevator to reach the depth of -480 m is 70 minutes.

Step-by-step explanation:

Let us consider the ground to be the origin (O), the height at which the elevator descends to be 'h' from the origin, and the depth the elevator goes to be 'd' from the origin.

The rate at which the elevator descends into a mine shaft be 'v'.

Given,

v = 7m/min,

h = 10 m

d = 480 m

To find,

The time (t) taken by the elevator to reach the depth (d).

Calculation,

The total distance traveled by elevator is s = (h + d)

s = 10 + 480 = 490 m

Now, speed = distance/time

v = s/t

7 m/min = 490m/t

t = 490m/7(m/min)

t = 70 min.

Therefore, the time taken by the elevator to reach the depth of -480 m is 70 minutes.

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