Math Problem Statement

A cannonball is fired from a cannon mounted on a platform. The height of the ball above the ground is given by h(t) = -4.9t^2 + 171.5t + 10.8, where h is the height in meters and t is the time in seconds. What is the maximum height of the cnanonball in metres? Round your answer to one decimal place, do not include units.

Solution

To find the maximum height of the cannonball, we need to find the vertex of the quadratic function h(t)=4.9t2+171.5t+10.8h(t) = -4.9t^2 + 171.5t + 10.8. The formula for the time at which the vertex occurs (the time when the maximum height is reached) in a quadratic function of the form ax2+bx+cax^2 + bx + c is given by:

tmax=b2at_{\text{max}} = \frac{-b}{2a}

In this case:

  • a=4.9a = -4.9
  • b=171.5b = 171.5

Substituting these values into the formula:

tmax=171.52(4.9)=171.59.817.5 secondst_{\text{max}} = \frac{-171.5}{2(-4.9)} = \frac{-171.5}{-9.8} \approx 17.5 \text{ seconds}

Now that we know the time at which the maximum height occurs, we substitute t=17.5t = 17.5 into the original height equation h(t)=4.9t2+171.5t+10.8h(t) = -4.9t^2 + 171.5t + 10.8 to find the maximum height:

h(17.5)=4.9(17.5)2+171.5(17.5)+10.8h(17.5) = -4.9(17.5)^2 + 171.5(17.5) + 10.8 h(17.5)=4.9(306.25)+171.5(17.5)+10.8h(17.5) = -4.9(306.25) + 171.5(17.5) + 10.8 h(17.5)=1500.125+3001.25+10.8h(17.5) = -1500.125 + 3001.25 + 10.8 h(17.5)=1512.925metersh(17.5) = 1512.925 \, \text{meters}

Therefore, the maximum height of the cannonball is approximately 1512.9 meters.

Would you like any further details or have any questions?

Related Questions:

  1. How would the height change if the coefficient of t2t^2 were positive instead of negative?
  2. What is the time when the cannonball hits the ground?
  3. How do we interpret the coefficient 171.5171.5 in the context of this problem?
  4. How would the equation change if the cannon were at a different initial height?
  5. What would happen to the maximum height if the cannonball was fired with less velocity?

Tip: The vertex formula for quadratics is key in finding maximum or minimum values, especially when the parabola opens downward (maximum) or upward (minimum).

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Math Problem Analysis

Mathematical Concepts

Quadratic Functions
Vertex of a Parabola
Maxima and Minima of Quadratic Functions

Formulas

Vertex formula for quadratic functions: t_max = -b / 2a

Theorems

The vertex of a quadratic function gives the maximum or minimum value of the function.

Suitable Grade Level

Grades 9-12