A soccer ball is kicked from the ground with an initial upward velocity of 90 feet per second. The equation h(t) = -16t^2+90t gives the height h of the ball after t seconds


a. How many seconds will it take for the ball to reach its maximum height


b. What is the maximum height of the ball


c. Give the domain and range of the function

Respuesta :

Answer:

The ball reaches a height of 126.58 ft after 2.8125 seconds

Step-by-step explanation:

The maximum height of a parabola can always be found by looking for the vertex. You can find the x value (or in this case the t value) of a vertex by using -b/2a in which a is the coefficient of x^2 and b is the coefficient of x.

-b/2a

-(90)/2(-16)

-90/-32

2.8125 seconds

Now to find the height, we input that value in for t

h = -16t^2 + 90t

h = -16(2.8125)^2 + 90(2.8125)

126.58 feet

Ball takes 2.8 seconds to reach maximum height

Maximum height of the ball is 126.56 feet

Domain : [tex]\left(0 \:,\:\infty \:\right)[/tex]

Range: [tex]\:[0\:,\:\frac{2025}{16}][/tex]

Given :

The equation h(t) = -16t^2+90t gives the height h of the ball after t seconds

Explanation :

To find the time when the ball reaches maximum height we use formula

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

From the given height equation , the value of a=-16  and b= 90

Replace it in the formula to find out 't'

[tex]t=\frac{-b}{2a} =\frac{-90}{2(-16)} =\frac{45}{16}=2.8 \; seconds[/tex]

It takes 2.8 seconds to reach maximum height

Now we plug in the value of 't' in h(t) to find out maximum height

[tex]h(t)=-16x^2+90x\\h(t)=-16(\frac{45}{16})^2+90(\frac{45}{16})\\H(\frac{45}{16})=\frac{2025}{16}[/tex]

Maximum height is 126.56 feet

Domain are the 't'  values for which the function is defined

't' represents seconds that cannot be 0

so domain is t>0

[tex]\left(0 \:,\:\infty \:\right)[/tex]

Range is the height that cannot be negative and it reaches maximum height

So range is h(t)>=0 and less than 126.56 feet

[tex]Range:\\ \:[0\:,\:\frac{2025}{16}][/tex]

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