Qestion in description

Question

The height in feet of an object dropped from an 18-foot stepladder is given by h(t)=−16t2+18, where t represents the time in seconds after the object is dropped. How long does it take the object to hit the ground? (Hint: The height is 0 when the object hits the ground. Round to the nearest hundredth of a second.)

Answer 1

h(t) = -16t2 + 18

 

The object is intially at a height of 18 feet when t = 0.  When the object hits the ground, its height is zero.  Set h(t) to zero and solve for t:

 

0 = -16t² + 18

16t² = 18

t² = 9/8

t = √(9/8) = (3/4)√2 seconds ≅ 1.06 sec.