Chapter 8: Problem 13
Solve the following initial value problems. $$y^{\prime}(t)-2 y=8, y(0)=0$$
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Chapter 8: Problem 13
Solve the following initial value problems. $$y^{\prime}(t)-2 y=8, y(0)=0$$
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One possible model that describes the free fall of an object in a gravitational field subject to air resistance uses the equation \(v^{\prime}(t)=g-b v,\) where \(v(t)\) is the velocity of the object for \(t \geq 0\), \(g=9.8 \mathrm{m} / \mathrm{s}^{2}\) is the acceleration due to gravity, and \(b>0\) is a constant that involves the mass of the object and the air resistance. a. Verify by substitution that a solution of the equation, subject to the initial condition \(v(0)=0,\) is \(v(t)=\frac{g}{b}\left(1-e^{-b t}\right)\). b. Graph the solution with \(b=0.1 s^{-1}\). c. Using the graph in part (c), estimate the terminal velocity \(\lim _{t \rightarrow \infty} v(t)\).
Consider the initial value problem \(y^{\prime}(t)=y^{n+1}, y(0)=y_{0},\) where \(n\) is a positive integer. a. Solve the initial value problem with \(n=1\) and \(y_{0}=1\) b. Solve the initial value problem with \(n=2\) and \(y_{0}=\frac{1}{\sqrt{2}}\) c. Solve the problem for positive integers \(n\) and \(y_{0}=n^{-1 / n}\) How do solutions behave as \(t \rightarrow 1^{-2}\)
Let \(y(t)\) be the population of a species that is being harvested, for \(t \geq 0 .\) Consider the harvesting model \(y^{\prime}(t)=0.008 y-h, y(0)=y_{0},\) where \(h\) is the annual harvesting rate, \(y_{0}\) is the initial population of the species, and \(t\) is measured in years. a. If \(y_{0}=2000,\) what harvesting rate should be used to maintain a constant population of \(y=2000,\) for \(t \geq 0 ?\) b. If the harvesting rate is \(h=200 /\) year, what initial population ensures a constant population?
A differential equation of the form \(y^{\prime}(t)=f(y)\) is said to be autonomous (the function \(f\) depends only on \(y\) ). The constant function \(y=y_{0}\) is an equilibrium solution of the equation provided \(f\left(y_{0}\right)=0\) (because then \(y^{\prime}(t)=0\) and the solution remains constant for all \(t\) ). Note that equilibrium solutions correspond to horizontal lines in the direction field. Note also that for autonomous equations, the direction field is independent of t. Carry out the following analysis on the given equations. a. Find the equilibrium solutions. b. Sketch the direction field, for \(t \geq 0\). c. Sketch the solution curve that corresponds to the initial condition \(y(0)=1\). $$y^{\prime}(t)=y(y-3)$$
Determine whether the following equations are separable. If so, solve the initial value problem. $$y^{\prime}(t)=e^{t y}, y(0)=1$$
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