Dropped from a cliff.

Question

A cliff is 36 feet above the water. If an object is dropped from the cliff, the formula h=36-16t^2 will give the height above the water's surface, in feet, of the object at t seconds from the time it was dropped. How many seconds does it take for an object dropped from the cliff to reach the water's surface? 

Answer 1

h(t) = 36 - 16t²

 

The object reaches the surface of the water when

 

h(t) = 0.

 

36 - 16t² = 0

 

16t² = 36

 

t² = 36/16

 

t = √(36/16) s = 6/4 s = 1.5 s

 

t = 1.5 s