Question 1

A portion of the direction field for the differential equation  = f(y) is shown below:

The dotted horizontal line has equation y = -7. Which of the following statements are true? Select all that apply.

Accepted Answer

A)   y(t)  = 0 is the solution to the initial-value problem  = f(y) , y(0)  = 0.
B)   y(t)  = -7 is the only equilibrium solution.
C)   There is no solution of the initial-value problem  = f(y) , y(0)  =  when  = -7.
D)   Every solution curve y(t)  is increasing toward a negative limit as t  →\rightarrow→   ∞\infty∞ .
E)   Every solution curve y(t)  tends towards -7 as t  →\rightarrow→   ∞\infty∞ .F) F(y)  cannot be a linear function of y.  B, E, F

Question 2

Newton's Law of Cooling states that the temperature of an object changes at a rate proportional to the difference between the temperature of the object itself and the temperature of its surroundings (typically the ambient temperature). Suppose the ambient temperature is 72°F and the rate constant is 0.11 per minute.What is the general solution of the differential equation for the temperature of the object, T(t), at any time t?

Accepted Answer

A)  
B)  
C)  
D)  
E)   D

Question 3

A model for the vertical flight of a projectile launched from the ground with velocity V in the absence of air resistance is
  
 From what single term in this equation can you infer the order of the equation?

Accepted Answer

The answer of A model for the vertical flight of...

Question 4

For what values of r is y(t) =  a solution of the differential equation  +4  - 12y = 0?

Accepted Answer

A)   2 and -6
B)   0 and 2
C)   -2 and 6
D)   0 and -6
E)   0, 2, and -6

Question 5

An antibiotic is being administered intravenously to a patient. Fluid containing 6.5 mg/ of the antibiotic enters the patient's bloodstream at a rate of 100 /hour. The antibiotic is absorbed by the body or otherwise leaves the bloodstream at a rate proportional to the amount present, with a rate constant of 0.4 per hour. Assume the antibiotic is always uniformly distributed throughout the bloodstream.Which of these is a differential equation for the amount of antibiotic, A(t), in the bloodstream at any time t?

Accepted Answer

A)  
B)  
C)  
D)

Question 6

Which of the following are solutions to the differential equation  - 16y = 0? Select all that apply.

Accepted Answer

A)  
B)  
C)  
D)  
E)  F) G) H)

Question 7

Consider the differential equation x =  + y.What is the value of the constant C in the general solution corresponding to the initial condition y(2) = 0?

Accepted Answer

The answer of Consider the differential equation x = ...

Question 8

Which of the following are solutions to the differential equation  - 2  = 0? Select all that apply

Accepted Answer

A)  
B)  
C)  
D)  
E)  F) G)

Question 9

Eight differential equations and four slope fields are given below

Which of the following are the zero isoclines for the differential equation in (A)? Select all that apply.

Accepted Answer

A)   y = 0
B)   y = 1
C)   y = -1
D)   y = t
E)   y = -t

Question 10

Which of the following pairs of values of A and B are such that all solutions of the differential equation  = Ay + B are such that  y(t) = 7? 
Select all that apply.

Accepted Answer

A)   A = -2, B = 14
B)   A = -7, B = 1
C)   A = -1, B = 7
D)   A = 1, B = -7
E)   A = -3, B = 21F)  A = -2, B = -14G)  A = 2, B = -14

Question 11

A model for the vertical flight of a projectile launched from the ground with velocity V in the absence of air resistance is 
  
Is this differential equation linear or nonlinear?

Accepted Answer

The answer of A model for the vertical flight of...

Question 12

A pond initially contains 150,000 gallons of water and an unknown amount of pesticide. Water containing 0.08 grams of pesticide per gallon flows into the pond at a rate of 400 gallons per hour. The mixture flows out of the pond at the same rate, so the amount of water in the pond remains constant. Assume the pesticide is uniformly mixed throughout the pond.How much pesticide will be in the pond after a very long time? ________ grams.

Accepted Answer

The answer of A pond initially contains 150,000 gallons of...

Question 13

A model for the vertical flight of a projectile launched from the ground with velocity V in the absence of air resistance is

Which of these initial conditions complete the description of the situation? Select all that apply.

Accepted Answer

A)  
B)  
C)  
D)  
E)

Question 14

A pond initially contains 70,000 gallons of water and an unknown amount of pesticide. Water containing 0.07 grams of pesticide per gallon flows into the pond at a rate of 360 gallons per hour. The mixture flows out of the pond at the same rate, so the amount of water in the pond remains constant. Assume the pesticide is uniformly mixed throughout the pond.
Which of these is the differential equation for the amount of pesticide, P(t), in the pond at any time t?

Accepted Answer

A)  
B)  
C)  
D)

Question 15

Consider the differential equation x  =  + y.
What is the general solution of this equation?

Accepted Answer

A)   y = C  + x
B)   y =  + Cx
C)   y = C(  + x) 
D)   y =  + x + C

Question 16

Newton's Law of Cooling states that the temperature of an object changes at a rate proportional to the difference between the temperature of the object itself and the temperature of its surroundings (typically the ambient temperature). Suppose the ambient temperature is 77°F and the rate constant is 0.09 per minute.Which of these is a differential equation for the temperature of the object, T(t), at any time t?

Accepted Answer

A)  
B)  
C)  
D)  
E)

Question 17

For each of the following partial differential equations, identify the order and indicate whether it is linear or nonlinear.

Accepted Answer

The answer of For each of the following partial differential...

Question 18

A pond initially contains 100,000 gallons of water and an unknown amount of pesticide. Water containing 0.07 grams of pesticide per gallon flows into the pond at a rate of 320 gallons per hour. The mixture flows out of the pond at the same rate, so the amount of water in the pond remains constant. Assume the pesticide is uniformly mixed throughout the pond.Which of these is the solution of the initial-value problem comprised of the differential equation for the amount of pesticide, P(t), in the pond at any time t and the initial condition P(0) = P0?

Accepted Answer

A)  0? 
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B)    
C)    
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Question 19

A pond initially contains 120,000 gallons of water and an unknown amount of pesticide. Water containing 0.08 grams of pesticide per gallon flows into the pond at a rate of 260 gallons per hour. The mixture flows out of the pond at the same rate, so the amount of water in the pond remains constant. Assume the pesticide is uniformly mixed throughout the pond.Which of these equations would you need to solve to find the time T (in hours) after which P(t) is within 2% of its limiting behavior?

Accepted Answer

A)  
B)  
C)  
D)

Question 20

An antibiotic is being administered intravenously to a patient. Fluid containing 4.5 mg/Cm3 of the antibiotic enters the patient's bloodstream at a rate of 100 Cm3/hour. The antibiotic is absorbed by the body or otherwise leaves the bloodstream at a rate proportional to the amount present, with a rate constant of 0.5 per hour. Assume the antibiotic is always uniformly distributed throughout the bloodstream.What is the general solution to the differential equation for the amount of antibiotic, A(t), in the bloodstream at any time t?

Accepted Answer

A)  3 of the antibiotic enters the patient's bloodstream at a rate of 100 Cm3/hour. The antibiotic is absorbed by the body or otherwise leaves the bloodstream at a rate proportional to the amount present, with a rate constant of 0.5 per hour. Assume the antibiotic is always uniformly distributed throughout the bloodstream.What is the general solution to the differential equation for the amount of antibiotic, A(t) , in the bloodstream at any time t? 
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B)  3 of the antibiotic enters the patient's bloodstream at a rate of 100 Cm3/hour. The antibiotic is absorbed by the body or otherwise leaves the bloodstream at a rate proportional to the amount present, with a rate constant of 0.5 per hour. Assume the antibiotic is always uniformly distributed throughout the bloodstream.What is the general solution to the differential equation for the amount of antibiotic, A(t) , in the bloodstream at any time t? 
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C)  3 of the antibiotic enters the patient's bloodstream at a rate of 100 Cm3/hour. The antibiotic is absorbed by the body or otherwise leaves the bloodstream at a rate proportional to the amount present, with a rate constant of 0.5 per hour. Assume the antibiotic is always uniformly distributed throughout the bloodstream.What is the general solution to the differential equation for the amount of antibiotic, A(t) , in the bloodstream at any time t? 
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D)  3 of the antibiotic enters the patient's bloodstream at a rate of 100 Cm3/hour. The antibiotic is absorbed by the body or otherwise leaves the bloodstream at a rate proportional to the amount present, with a rate constant of 0.5 per hour. Assume the antibiotic is always uniformly distributed throughout the bloodstream.What is the general solution to the differential equation for the amount of antibiotic, A(t) , in the bloodstream at any time t? 
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E)  3 of the antibiotic enters the patient's bloodstream at a rate of 100 Cm3/hour. The antibiotic is absorbed by the body or otherwise leaves the bloodstream at a rate proportional to the amount present, with a rate constant of 0.5 per hour. Assume the antibiotic is always uniformly distributed throughout the bloodstream.What is the general solution to the differential equation for the amount of antibiotic, A(t) , in the bloodstream at any time t? 
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Exam 1: Introduction

A model for the vertical flight of a projectile launched from the ground with velocity V in the absence of air resistance is From what single term in this equation can you infer the order of the equation?

For what values of r is y(t) = a solution of the differential equation +4 - 12y = 0?

Which of the following are solutions to the differential equation - 16y = 0? Select all that apply.

Consider the differential equation x = + y.What is the value of the constant C in the general solution corresponding to the initial condition y(2) = 0?

Which of the following are solutions to the differential equation - 2 = 0? Select all that apply

Eight differential equations and four slope fields are given below Which of the following are the zero isoclines for the differential equation in (A) ? Select all that apply.

Which of the following pairs of values of A and B are such that all solutions of the differential equation = Ay + B are such that y(t) = 7? Select all that apply.

A model for the vertical flight of a projectile launched from the ground with velocity V in the absence of air resistance is Is this differential equation linear or nonlinear?

A model for the vertical flight of a projectile launched from the ground with velocity V in the absence of air resistance is Which of these initial conditions complete the description of the situation? Select all that apply.

Consider the differential equation x = + y. What is the general solution of this equation?

For each of the following partial differential equations, identify the order and indicate whether it is linear or nonlinear.