Math Problem Statement

A model rocket is launched upward with an initial velocity of 210 feet per second. The height, in feet, of the rocket t seconds after the launch is given by 

h = −16t2 + 210t.

 How many seconds after the launch will the rocket be 370 feet above the ground? Round to the nearest tenth of a second. (Enter your answers as a comma-separated list.)

Solution

To determine the time(s) tt when the rocket reaches a height of 370 feet, we can use the given height equation:

h(t)=16t2+210th(t) = -16t^2 + 210t

We want to find the value of tt when h(t)=370h(t) = 370 feet. So, we set up the equation:

370=16t2+210t370 = -16t^2 + 210t

This can be rearranged to:

16t2+210t370=0-16t^2 + 210t - 370 = 0

This is a quadratic equation in the form at2+bt+c=0at^2 + bt + c = 0, where:

  • a=16a = -16
  • b=210b = 210
  • c=370c = -370

We can solve this quadratic equation using the quadratic formula:

t=b±b24ac2at = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

Substituting the values of aa, bb, and cc:

t=210±(210)24(16)(370)2(16)t = \frac{-210 \pm \sqrt{(210)^2 - 4(-16)(-370)}}{2(-16)} t=210±441002368032t = \frac{-210 \pm \sqrt{44100 - 23680}}{-32} t=210±2042032t = \frac{-210 \pm \sqrt{20420}}{-32} t=210±142.932t = \frac{-210 \pm 142.9}{-32}

This gives us two possible solutions:

  1. t1=210+142.932=67.1322.1t_1 = \frac{-210 + 142.9}{-32} = \frac{-67.1}{-32} \approx 2.1 seconds
  2. t2=210142.932=352.93211.0t_2 = \frac{-210 - 142.9}{-32} = \frac{-352.9}{-32} \approx 11.0 seconds

So, the rocket will be 370 feet above the ground at approximately 2.1 seconds and 11.0 seconds after launch.

Would you like more details or have any questions? Here are some related questions:

  1. What is the maximum height reached by the rocket?
  2. How long does it take for the rocket to reach its maximum height?
  3. At what time will the rocket return to the ground?
  4. What is the significance of the coefficient 16-16 in the equation?
  5. How would the time change if the height was 500 feet instead of 370 feet?

Tip: The quadratic formula is a reliable method for solving any quadratic equation, especially when it cannot be easily factored.

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Math Problem Analysis

Mathematical Concepts

Quadratic Equations
Projectile Motion

Formulas

Quadratic equation formula: ax^2 + bx + c = 0

Theorems

Quadratic formula

Suitable Grade Level

High School