A ladder of length `17m` rests with one end agains a vertical wall and the other on the vessel ground. If the lower end slips away at the rate of `1ms^(-1)` , then when it is `8m` away from the wall, its upper end is coming down at the rate of

Options

A. `5/8 ms^(-1)`
B. `-8/15 ms^(-1)`
C. `(5 pi)/4ms^(-1)`
D. `8/5 ms^(-1)`

Answer

B

Explanation

When `a=8, b=15`
Then `a^(2)+b^(2)=17^(2)`
`:.2a (da)/(dt)+2b (db)/(dt)=0`
`:.8(1)+15(db)/(dt)=0`
`:.(db)/(dt)=(-8)/15ms^(-1)`.