Math Problem Statement

NASA launches a rocket at t = 0 seconds. Its height, in meters above sea-level, as a function of time is given by h(t) = -4.9t^2 + 205t + 304. Assuming that the rocket will splash down into the ocean, at what time does splashdown occur? How high above sea-level does the rocket get at its peak?

Solution

To solve the two questions:

The height of the rocket as a function of time is given by:

h(t)=4.9t2+205t+304h(t) = -4.9t^2 + 205t + 304

1. Time of Splashdown:

The rocket splashes down when its height becomes zero (h(t)=0h(t) = 0). Solve for tt using the quadratic equation:

4.9t2+205t+304=0-4.9t^2 + 205t + 304 = 0

The quadratic formula is:

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

Here:

  • a=4.9a = -4.9
  • b=205b = 205
  • c=304c = 304

Substitute into the formula:

t=205±20524(4.9)(304)2(4.9)t = \frac{-205 \pm \sqrt{205^2 - 4(-4.9)(304)}}{2(-4.9)}

t=205±42025+5958.49.8t = \frac{-205 \pm \sqrt{42025 + 5958.4}}{-9.8}

t=205±47983.49.8t = \frac{-205 \pm \sqrt{47983.4}}{-9.8}

t=205±219.029.8t = \frac{-205 \pm 219.02}{-9.8}

This gives two solutions: t=205+219.029.8andt=205219.029.8t = \frac{-205 + 219.02}{-9.8} \quad \text{and} \quad t = \frac{-205 - 219.02}{-9.8}

Calculating each: t1=14.029.81.43(not valid as time cannot be negative)t_1 = \frac{14.02}{-9.8} \approx -1.43 \, \text{(not valid as time cannot be negative)}

t2=424.029.843.27secondst_2 = \frac{-424.02}{-9.8} \approx 43.27 \, \text{seconds}

So, the rocket splashes down after approximately 43.27 seconds.


2. Peak Height:

The rocket reaches its peak when the vertical velocity becomes zero. The velocity is the derivative of h(t)h(t):

v(t)=dhdt=9.8t+205v(t) = \frac{dh}{dt} = -9.8t + 205

Set v(t)=0v(t) = 0 to find the time at the peak: 9.8t+205=0-9.8t + 205 = 0

t=2059.820.92secondst = \frac{205}{9.8} \approx 20.92 \, \text{seconds}

Substitute t=20.92t = 20.92 into h(t)h(t) to find the peak height:

h(20.92)=4.9(20.92)2+205(20.92)+304h(20.92) = -4.9(20.92)^2 + 205(20.92) + 304

First, calculate (20.92)2437.86(20.92)^2 \approx 437.86: h(20.92)=4.9(437.86)+205(20.92)+304h(20.92) = -4.9(437.86) + 205(20.92) + 304

h(20.92)=2145.51+4288.6+304h(20.92) = -2145.51 + 4288.6 + 304

h(20.92)2447.09metersh(20.92) \approx 2447.09 \, \text{meters}

So, the rocket peaks at approximately 2447.09 meters.


Final Answers:

  1. The rocket splashes down after 43.27 seconds.
  2. The rocket peaks at 2447.09 meters above sea-level.

Would you like detailed step-by-step explanations for these solutions?


Related Questions:

  1. What is the initial height of the rocket at t=0t = 0?
  2. How long does it take for the rocket to reach 1000 meters?
  3. What is the velocity of the rocket at splashdown?
  4. How would the results change if air resistance is considered?
  5. What is the acceleration of the rocket throughout its motion?

Tip:

When solving quadratic equations, always check if the discriminant (b24acb^2 - 4ac) is positive to ensure real solutions.

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Math Problem Analysis

Mathematical Concepts

Quadratic Equations
Derivatives
Physics (Projectile Motion)

Formulas

Quadratic formula: t = (-b ± √(b² - 4ac)) / 2a
Derivative to find the peak: v(t) = dh/dt = -9.8t + 205

Theorems

Quadratic Formula
Maximization using Derivatives

Suitable Grade Level

Grades 9-12