Answer: 8.73 ft/s
Step-by-step explanation:
We have the following equation that models the motion of the rock:

Where
is the height of the rock at a time
.
Now, if
we can find
and then the velocity of the rock at that height:

Rearranging the equation:

Multiplying the equation by -1:

Solving with the quadratic formula
, where
,
,
.

Choosing the positive result of the equation:
Since velocity
is defined as the traveled distance
in a given time
, we have:


This is the velocity of the rock at the height of 48 feet