Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 8 - Section 8.4 - Plane Curves and Parametric Equations - 8.4 Exercises - Page 617: 38

Answer

(a) $64s$ (b) $113512ft$ (c) $16384ft$

Work Step by Step

(a) Step 1. List the given parametric equations: $x=(v_0cos\alpha)t, y=(v_0sin\alpha)t-16t^2$ Step 2. With the initial conditions $v_0=2048ft/s, \alpha=30^{\circ}$, let $y(t)=0$ for the moment when the bullet hit the ground, we have $2048sin30^{\circ}t-16t^2=0$ which gives $t=64s$ (we throw away t=0 as it is the starting point.) (b) The total distance is given by the x-value at t=64s: $x=2048cos30^{\circ}\times64\approx113512ft$ (c) The maximum height is reached at half of the total travel time $t1=\frac{64}{2}=32s$ which gives $y=2048sin30^{\circ}\times32-16\times32^2=16384ft$
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