A projectile is fired straight upward with an initial velocity of 400 feet per second. The height of the projectile, [tex]\( h(t) \)[/tex], is represented by the function [tex] h(t) = -16t^2 + 400t [/tex], where [tex]\( t \)[/tex] is the time in seconds.

What is the maximum height of the object?

A. 12.5 feet
B. 25 feet
C. 400 feet
D. 2500 feet



Answer :

To determine the maximum height of the projectile, we need to analyze the quadratic function given: [tex]\( h(t) = -16t^2 + 400t \)[/tex]. This function represents the height of the projectile at any given time [tex]\( t \)[/tex].

### Step-by-step Solution:

1. Identify the Coefficients:
The quadratic function is in the standard form [tex]\( h(t) = at^2 + bt + c \)[/tex], where [tex]\( a = -16 \)[/tex], [tex]\( b = 400 \)[/tex], and [tex]\( c = 0 \)[/tex].

2. Determine the Vertex:
The maximum height of a projectile in a parabolic path occurs at the vertex of the parabola. For a parabola represented by [tex]\( at^2 + bt + c \)[/tex], the time [tex]\( t \)[/tex] at which the maximum height occurs is found using the formula:
[tex]\[ t = -\frac{b}{2a} \][/tex]

Plugging in the values for [tex]\( a \)[/tex] and [tex]\( b \)[/tex]:
[tex]\[ t = -\frac{400}{2 \cdot -16} = \frac{400}{32} = 12.5 \][/tex]
Thus, the time at which the projectile reaches its maximum height is [tex]\( t = 12.5 \)[/tex] seconds.

3. Calculate the Maximum Height:
Substitute [tex]\( t = 12.5 \)[/tex] back into the height function to find the maximum height:
[tex]\[ h(12.5) = -16 (12.5)^2 + 400(12.5) \][/tex]
Simplify inside the parentheses:
[tex]\[ (12.5)^2 = 156.25 \][/tex]
Then multiply:
[tex]\[ -16 \cdot 156.25 = -2500 \][/tex]
And:
[tex]\[ 400 \cdot 12.5 = 5000 \][/tex]
Adding these together:
[tex]\[ h(12.5) = -2500 + 5000 = 2500 \][/tex]
Hence, the maximum height of the projectile is [tex]\( 2500 \)[/tex] feet.

### Conclusion:
The maximum height of the object is:
2500 feet