Question

An object is dropped from a bridge and allowed to freefall to the ground. The height of the object over time can be modeled using h(t)=144-16t2.

How many seconds will it take the object to reach the ground?

2 seconds
3 seconds
9 seconds
16 seconds
\

Answer 1

3 seconds

Explanation:

when the stone reaches the ground then h = 0 , that is

144 - 16t² = 0 ( subtract 144 from both sides )

- 16t² = - 144 ( divide both sides by - 16 )

t² =
`(-144)/(-16)` = 9 ( take square root of both sides )

`√(t^2)` = ±
`√(9)` , that is

t = ± 3

however, t must be positive, then t = 3

the object takes 3 seconds to reach the ground