Chapter 10.4, Problem 46E

To determine

Find the solution.

Answer to Problem 46E

  $1.5$ seconds

Explanation of Solution

Given Information: $h=-16t^2+50$

Formula Used: Quadratic formula

Calculation:

The quadratic equation gives the height of the crow from its starting position, which is 50 feet above ground.

  $h=-16t^2+50$

To find time it takes to 15 feet, above the ground level, where height is equal to $h=15$

  $16t^2=-h+50$

So, simplify

  $t^2=\frac{-15+50}{16}$

Now, square root both sides.

  $t=\frac{\sqrt{35}}{\sqrt{16}}$

Now,

  $t=\frac{\sqrt{5\times 7}}{\sqrt{2\times 2\times 2\times 2}}$

Now, pair of prime numbers given out

  $t=\frac{\sqrt{35}}{4}$

Hence,

  $t=1.5$ seconds

So, it takes the crow about $1.5$ seconds to 15 feet, above the ground level, fall from its starting position, which is 50 feet.