Exam 9: Differential Equations
Exam 1: Functions and Limits117 Questions
Exam 2: Derivatives151 Questions
Exam 3: Applications of Differentiation153 Questions
Exam 4: Integrals95 Questions
Exam 5: Applications of Integration120 Questions
Exam 6: Inverse Functions127 Questions
Exam 7: Techniques of Integration124 Questions
Exam 8: Further Applications of Integration86 Questions
Exam 9: Differential Equations67 Questions
Exam 10: Parametric Equations and Polar Coordinates72 Questions
Exam 11: Infinite Sequences and Series158 Questions
Exam 12: Vectors and the Geometry of Space60 Questions
Exam 13: Vector Functions93 Questions
Exam 14: Partial Derivatives132 Questions
Exam 15: Multiple Integrals124 Questions
Exam 16: Vector Calculus137 Questions
Exam 17: Second-Order Differential Equations63 Questions
Exam 18: Final Exam44 Questions
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Which of the following functions are the constant solutions of the equation
a.
b.
c.
d.
e. 
(Short Answer)
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Let c be a positive number. A differential equation of the form
where k is a positive constant, is called a doomsday equation because the exponent in the expression
is larger than the exponent 1for natural growth. An especially prolific breed of rabbits has the growth term
. If
such rabbits breed initially and the warren has
rabbits after
months, then when is doomsday?
(Essay)
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Kirchhoff's Law gives us the derivative equation
.
If
, use Euler's method with step size 0.1 to estimate
after 0.3 second.
(Short Answer)
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The population of the world was about 5.3 billion in 1990. Birth rates in the 1990s range from 35 to 40 million per year and death rates range from 15 to 20 million per year. Let's assume that the carrying capacity for world population is 100 billion. Use the logistic model to predict the world population in the 2,450 year. Calculate your answer in billions to one decimal place. (Because the initial population is small compared to the carrying capacity, you can take k to be an estimate of the initial relative growth rate.)
(Multiple Choice)
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Suppose that a population grows according to a logistic model with carrying capacity
and
per year. Choose the logistic differential equation for these data.
(Multiple Choice)
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An object with mass m is dropped from rest and we assume that the air resistance is proportional to the speed of the object. If
is the distance dropped after t seconds, then the speed is
and the acceleration is
. If g is the acceleration due to gravity, then the downward force on the object is
, where c is a positive constant, and Newton's Second Law gives
.
Find the limiting velocity.
(Essay)
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The solution of the differential equation
satisfies the initial condition
.
Find the limit. 
(Short Answer)
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In the circuit shown in Figure, a generator supplies a voltage of
volts, the inductance is 2 H, the resistance is 40
, and
. Find the current 0.2 s after the switch is closed. Round your answer to two decimal places. 
(Multiple Choice)
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Let
be the performance level of someone learning a skill as a function of the training time t. The graph of P is called a learning curve. We propose the differential equation
as a reasonable model for learning, where r is a positive constant. Solve it as a linear differential equation.
(Multiple Choice)
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Select a direction field for the differential equation
from a set of direction fields labeled I-IV. 
(Short Answer)
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Let c be a positive number. A differential equation of the form
where k is a positive constant is called a doomsday equation because the exponent in the expression
is larger than the exponent 1 for natural growth. An especially prolific breed of rabbits has the growth term
. If
such rabbits breed initially and the warren has
rabbits after
months, then when is doomsday?
(Multiple Choice)
4.8/5
(83)
We modeled populations of aphids and ladybugs with a Lotka-Volterra system. Suppose we modify those equations as follows:
, 
(Multiple Choice)
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