Question

An elevator descends into a mine shaft at the rate of 5 metre per minute
A) what will be its position after 1 hour
B) if it begins to descends from 15m above the ground level what will be its position after 45 minutes
C) if the descent starts from 20m above the ground level. How long will it take to reach -370m

Answer 1

Sol : √8 + 4√32 - 6√2

     = √(2 x 2 x 2 ) + 4√( 2 x 2 x 2 x 2 x 2 ) - 6√2

    = √( 4 x 2 )  + 4√( 16 x 2 ) - 6√2

We have √4 = 2 and √16 = 4.

Now,
    = 2√2 + 4 x 4 √2 - 6√2

   = 2√2 + 16√2 - 6√2

   = √2 ( 2 + 16 - 6 )

  = √2 ( 18 - 6 )

  = √2 x 12

  = 12√2.Ans.