Math Problem Statement

The height y (in feet) of a ball thrown by a child is y = -1/16x^2 + 6x + 3, where x is the horizontal distance in feet from the point at which the ball is thrown. (a) How high is the ball when it leaves the child's hand? (b) What is the maximum height of the ball? (c) How far from the child does the ball strike the ground?

Solution

The equation provided in the question is:

y=116x2+6x+3y = -\frac{1}{16}x^2 + 6x + 3

Where yy is the height of the ball and xx is the horizontal distance from the point of throw.

Let's break down each part of the question:

(a) How high is the ball when it leaves the child's hand?

To find the height when the ball leaves the child's hand, we need to substitute x=0x = 0 into the equation because this is the point where the ball is thrown (initial horizontal distance).

y=116(0)2+6(0)+3=3y = -\frac{1}{16}(0)^2 + 6(0) + 3 = 3

So, the ball is 3 feet high when it leaves the child's hand.

(b) What is the maximum height of the ball?

The equation is a quadratic equation, and the maximum height will occur at the vertex. The formula to find the xx-coordinate of the vertex for a quadratic equation y=ax2+bx+cy = ax^2 + bx + c is:

x=b2ax = -\frac{b}{2a}

In this case, a=116a = -\frac{1}{16} and b=6b = 6, so:

x=62×116=48x = -\frac{6}{2 \times -\frac{1}{16}} = 48

Now, substitute x=48x = 48 into the equation to find the maximum height:

y=116(48)2+6(48)+3y = -\frac{1}{16}(48)^2 + 6(48) + 3 y=116(2304)+288+3=144+288+3=147y = -\frac{1}{16}(2304) + 288 + 3 = -144 + 288 + 3 = 147

So, the maximum height of the ball is 147 feet.

(c) How far from the child does the ball strike the ground?

The ball strikes the ground when y=0y = 0. We need to solve the equation:

0=116x2+6x+30 = -\frac{1}{16}x^2 + 6x + 3

Multiply the entire equation by 16 to eliminate the fraction:

0=x2+96x+480 = -x^2 + 96x + 48

Now, solve this quadratic equation using the quadratic formula:

x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} where a=1a = -1, b=96b = 96, and c=48c = 48.

x=96±9624(1)(48)2(1)x = \frac{-96 \pm \sqrt{96^2 - 4(-1)(48)}}{2(-1)} x=96±9216+1922x = \frac{-96 \pm \sqrt{9216 + 192}}{-2} x=96±94082x = \frac{-96 \pm \sqrt{9408}}{-2} x=96±97.982x = \frac{-96 \pm 97.98}{-2}

This gives two solutions for xx:

x1=96+97.9821.9820.99(not valid, since distance cannot be negative)x_1 = \frac{-96 + 97.98}{-2} \approx \frac{1.98}{-2} \approx -0.99 \quad (\text{not valid, since distance cannot be negative}) x2=9697.982193.98296.99x_2 = \frac{-96 - 97.98}{-2} \approx \frac{-193.98}{-2} \approx 96.99

So, the ball strikes the ground about 97 feet from the child.


Do you have any questions or want more details?

Here are 5 related questions:

  1. How do you determine the vertex of a quadratic function?
  2. Why is there a negative sign in front of the x2x^2 term?
  3. How can you solve a quadratic equation without using the quadratic formula?
  4. What is the significance of the discriminant in the quadratic formula?
  5. How does the height equation change if the child throws the ball with more force?

Tip: Always check the sign of the x2x^2 term in a quadratic equation to understand whether the parabola opens upwards or downwards (which helps determine if it's a maximum or minimum).

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Quadratic Functions
Vertex of a Parabola
Roots of Quadratic Equations

Formulas

y = ax^2 + bx + c (Standard form of a quadratic equation)
Vertex formula: x = -b / (2a)
Quadratic formula: x = (-b ± √(b^2 - 4ac)) / (2a)

Theorems

Quadratic Formula
Vertex Theorem for Quadratic Functions

Suitable Grade Level

Grades 9-12