Math Problem Statement

A snorkeler dives for a shell on a reef. After entering the water, the diver descends 7/2 ft in one second. Write an equation for a parabola that models the diver's vertical position y with respect to time x.

Solution

The problem asks for an equation modeling the diver's vertical position, yy, in terms of time, xx, with a given rate of descent.

Information from the problem:

  • The diver descends at a rate of 72\frac{7}{2} feet per second.
  • There is a parabolic path (indicating quadratic motion).
  • At x=0x = 0, y=0y = 0 (since the diver starts at the surface).
  • There are two key points from the diagram:
    • (3,0)(3, 0), when the diver starts descending from the surface at 3 seconds.
    • (17,0)(17, 0), when the diver is at 0 feet again at 17 seconds.

Equation of the parabola:

Since the diver returns to the same vertical level (0 feet) after 17 seconds, this suggests a quadratic equation in standard form:

y=a(x3)(x17)y = a(x - 3)(x - 17)

Now, we need to determine the constant aa. We know that the rate of descent is 72\frac{7}{2} feet per second at x=1x = 1 second after the diver starts descending. Let's use this information to calculate aa.

At x=4x = 4 seconds, the diver has descended by 72×1=72\frac{7}{2} \times 1 = \frac{7}{2}. Let's plug this into the equation to find aa:

72=a(43)(417)\frac{7}{2} = a(4 - 3)(4 - 17) 72=a(1)(13)\frac{7}{2} = a(1)(-13) 72=13a\frac{7}{2} = -13a a=726a = -\frac{7}{26}

Final Equation:

y=726(x3)(x17)y = -\frac{7}{26}(x - 3)(x - 17)

This is the equation modeling the diver's vertical position yy with respect to time xx.

Would you like more details or have any other questions?

Related Questions:

  1. How do you derive the equation of a parabola from two points and a slope?
  2. How does the rate of descent influence the shape of the parabolic curve?
  3. What does the vertex of the parabola represent in this context?
  4. Can you calculate the maximum depth the diver reaches?
  5. How do changes in the descent rate affect the coefficients in the equation?

Tip:

Always check the units and signs of your constants to ensure they match the physical context of the problem, especially in motion problems!

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Parabolic Motion

Formulas

y = a(x - p)(x - q)

Theorems

Roots of a Quadratic Equation
Parabolic Motion

Suitable Grade Level

Grade 9-10