Question

Tara and Mallory are practicing their passing at a volleyball practice. Tara bumps the ball from a height of 3 feet above the ground with an initial upward velocity of 12 feet/second. at the same time, mallory serves the ball from a height of 3.25 feet above the ground with an initial upward velocity of 9 feet/second.

if x represents the number of seconds since each ball is passed and y represents the height of the ball, which system of equations models the projectile motion of the two balls? recall that the acceleration due to gravity is -32 feet/second

Answer 1

The system of equation that models the projectile of the two balls is option;

C. y = -16·x² + 12·x + 3

y = -16·x² + 9·x + 3.25

Explanation:

The general equation for vertical (upward) motion under gravity is presented as follows;

h - h₀ = u·t + 1/2·g·t²

Where;

h = The final height reached

h₀ = The initial height

u = The initial velocity

g = The acceleration due to gravity ≈ -32 feet/second

t = The time taken

We can rewrite the above equation with different letters for the variables as follows;

h = y,

h₀ = y₀, and

t = x

Therefore, we have;

y - y₀ = u·x - 1/2 × 32 × x²

y = u·x - 1/2 × 32 × x² + y₀ = u·x - 16· x² + y₀

y = u·x - 16· x² + y₀ = -16·x² + u·x + y₀

y = -16·x² + u·x + y₀

For Tara, we have;

u = 12 feet/second

y₀ = 3 feet

Therefore, we get;

y = -16·x² + 12·x + 3

For Mallory, we have;

u = 9 feet/second

y₀ = 3.25 feet

Therefore, we get;

y = -16·x² + 9·x + 3.25

The correct option is therefore;

y = -16·x² + 12·x + 3

y = -16·x² + 9·x + 3.25