[填空题]
John drops a stone from theq(/os/x ) eb47pikcrr3 aioq;(m,nz)eyn()m3x oszktop of a cliff which is h metres above sea level. The stone strikes the water surface after 9 seconds. The velocity of the falling s(n3 ;az3)i me)qny xm,oz(okstone, $v \mathrm{~m} \mathrm{~s}^{-1}$, t seconds after John releases it, can be modelled by the function
1. Find the velocity of the stone when t=12 , giving your answer to the nearest $ \mathrm{m} \mathrm{s}^{-1}$ . ≈
2. Calculate the value of h , giving your answer to the nearest metre.≈
The velocity of the stone when it reaches the bottom of sea is 10 $\mathrm{~m} \mathrm{~s}^{-1}$ .
3. Determine the depth of sea near the cliff, giving your answer to the nearest metre.≈
