A volleyball is served by a 6-foot player at an initial upward velocity of 33 feet per second. The situation is modeled by the equation h=−16t2+33t+6

h representing the height in feet and t representing the time in seconds. Using this equation, define the domain of the ball when it reaches its maximum height.(1 point)
Responses

23.01 feet
23.01 feet

1.03 seconds
1.03 seconds

1.22 seconds
1.22 seconds

−1.03 seconds

1 answer

To find the time when the volleyball reaches its maximum height, we can use the vertex formula for a quadratic equation of the form \( h = at^2 + bt + c \). The time at which the maximum height occurs can be found using the formula:

\[ t = -\frac{b}{2a} \]

In this equation, \( a = -16 \) and \( b = 33 \).

Substituting the values in gives:

\[ t = -\frac{33}{2(-16)} = \frac{33}{32} \approx 1.03125 \text{ seconds} \approx 1.03 \text{ seconds} \]

Now, regarding the domain, the volleyball will be served at \( t = 0 \) seconds, and it will reach the ground when the height \( h \) is equal to 0. To determine when the ball hits the ground, we can solve for \( t \) when \( h = 0 \):

\[ -16t^2 + 33t + 6 = 0 \]

Using the quadratic formula \( t = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \), where \( a = -16, b = 33, c = 6 \):

  1. Calculate the discriminant:

\[ b^2 - 4ac = 33^2 - 4(-16)(6) = 1089 + 384 = 1473 \]

  1. Now apply the quadratic formula:

\[ t = \frac{-33 \pm \sqrt{1473}}{2 \times -16} \] \[ t \approx \frac{-33 \pm 38.41}{-32} \]

Calculating the two possible times:

  1. Using the positive root:

\[ t = \frac{-33 + 38.41}{-32} \approx \frac{5.41}{-32} \approx -0.169 \text{ (not valid since time cannot be negative)} \]

  1. Using the negative root:

\[ t = \frac{-33 - 38.41}{-32} \approx \frac{-71.41}{-32} \approx 2.23 \text{ seconds} \]

Now, the domain of the volleyball is from \( t = 0 \) to \( t \approx 2.23 \) seconds.

Thus, the ball reaches its maximum height at approximately 1.03 seconds. This means the correct response from the options you provided is:

1.03 seconds.