Calculus 1 : Rate of Change

Study concepts, example questions & explanations for Calculus 1

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Example Questions

Example Question #241 : Rate Of Change

A spherical balloon is being filled with air. What is ratio of the rate of growth of the volume of the sphere to the rate of growth of the surface area when the radius is one half?

Possible Answers:

\(\displaystyle \frac{1}{4}\)

\(\displaystyle 2\)

\(\displaystyle \frac{1}{2}\)

\(\displaystyle 4\)

\(\displaystyle 1\)

Correct answer:

\(\displaystyle \frac{1}{4}\)

Explanation:

Let's begin by writing the equations for the volume and surface area of a sphere with respect to the sphere's radius:

\(\displaystyle V=\frac{4}{3}\pi r^3\)

\(\displaystyle A=4\pi r^2\)

The rates of change can be found by taking the derivative of each side of the equation with respect to time:

\(\displaystyle \frac{dV}{dt}=4\pi r^2 \frac{dr}{dt}\)

\(\displaystyle \frac{dA}{dt}=8\pi r \frac{dr}{dt}\)

The rate of change of the radius is going to be the same for the sphere regardless of the considered parameter. To find the ratio of the rates of changes of the volume and surface area, divide:

\(\displaystyle 4\pi r^2 \frac{dr}{dt}=(\phi)8\pi r \frac{dr}{dt}\)

\(\displaystyle \phi =\frac{\frac{1}{2}}{2}\)

\(\displaystyle \phi =\frac{1}{4}\)

Example Question #241 : Rate Of Change

A spherical balloon is deflating, although it retains a spherical shape. What is ratio of the rate of loss of the volume of the sphere to the rate of loss of the circumference when the radius is 5?

Possible Answers:

\(\displaystyle 50\)

\(\displaystyle 5\)

\(\displaystyle 15\)

\(\displaystyle 10\)

\(\displaystyle 25\)

Correct answer:

\(\displaystyle 50\)

Explanation:

Let's begin by writing the equations for the volume and circumference of a sphere with respect to the sphere's radius:

\(\displaystyle V=\frac{4}{3}\pi r^3\)

\(\displaystyle C=2\pi r^\)

The rates of change can be found by taking the derivative of each side of the equation with respect to time:

\(\displaystyle \frac{dV}{dt}=4\pi r^2 \frac{dr}{dt}\)

\(\displaystyle \frac{dC}{dt}=2\pi \frac{dr}{dt}\)

The rate of change of the radius is going to be the same for the sphere regardless of the considered parameter. To find the ratio of the rates of changes of the volume and circumference, divide:

\(\displaystyle 4\pi r^2 \frac{dr}{dt}=(\phi)2\pi \frac{dr}{dt}\)

\(\displaystyle \phi =2r^2\)

\(\displaystyle \phi =50\)

Example Question #243 : Rate Of Change

A spherical balloon is being filled with air. What is ratio of the rate of growth of the volume of the sphere to the rate of growth of the circumference when the radius is 3?

Possible Answers:

\(\displaystyle 18\)

\(\displaystyle 9\)

\(\displaystyle 3\)

\(\displaystyle 12\)

\(\displaystyle 6\)

Correct answer:

\(\displaystyle 18\)

Explanation:

Let's begin by writing the equations for the volume and circumference of a sphere with respect to the sphere's radius:

\(\displaystyle V=\frac{4}{3}\pi r^3\)

\(\displaystyle C=2\pi r^\)

The rates of change can be found by taking the derivative of each side of the equation with respect to time:

\(\displaystyle \frac{dV}{dt}=4\pi r^2 \frac{dr}{dt}\)

\(\displaystyle \frac{dC}{dt}=2\pi \frac{dr}{dt}\)

The rate of change of the radius is going to be the same for the sphere regardless of the considered parameter. To find the ratio of the rates of changes of the volume and circumference, divide:

\(\displaystyle 4\pi r^2 \frac{dr}{dt}=(\phi)2\pi \frac{dr}{dt}\)

\(\displaystyle \phi =2r^2\)

\(\displaystyle \phi =18\)

Example Question #2121 : Functions

A spherical balloon is being filled with air. What is ratio of the rate of growth of the surface area of the sphere to the rate of growth of the circumference when the radius is 6?

Possible Answers:

\(\displaystyle 24\pi\)

\(\displaystyle 12\)

\(\displaystyle 12\pi\)

\(\displaystyle 24\)

\(\displaystyle 6\pi\)

Correct answer:

\(\displaystyle 24\)

Explanation:

Let's begin by writing the equations for the surface area and circumference of a sphere with respect to the sphere's radius:

\(\displaystyle A=4\pi r^2\)

\(\displaystyle C=2\pi r\)

The rates of change can be found by taking the derivative of each side of the equation with respect to time:

\(\displaystyle \frac{dA}{dt}=8\pi r \frac{dr}{dt}\)

\(\displaystyle \frac{dC}{dt}=2\pi \frac{dr}{dt}\)

The rate of change of the radius is going to be the same for the sphere regardless of the considered parameter. To find the ratio of the rates of changes of the surface area and circumference, divide:

\(\displaystyle 8\pi r \frac{dr}{dt}=(\phi)2\pi \frac{dr}{dt}\)

\(\displaystyle \phi =4r\)

\(\displaystyle \phi =24\)

Example Question #3152 : Calculus

A spherical balloon is deflating, although it retains a spherical shape. What is ratio of the rate of loss of the surface area of the sphere to the rate of loss of the circumference when the radius is 13?

Possible Answers:

\(\displaystyle 26\)

\(\displaystyle 52\pi\)

\(\displaystyle 104\pi\)

\(\displaystyle 52\)

\(\displaystyle 26\pi\)

Correct answer:

\(\displaystyle 52\)

Explanation:

Let's begin by writing the equations for the surface area and circumference of a sphere with respect to the sphere's radius:

\(\displaystyle A=4\pi r^2\)

\(\displaystyle C=2\pi r\)

The rates of change can be found by taking the derivative of each side of the equation with respect to time:

\(\displaystyle \frac{dA}{dt}=8\pi r \frac{dr}{dt}\)

\(\displaystyle \frac{dC}{dt}=2\pi \frac{dr}{dt}\)

The rate of change of the radius is going to be the same for the sphere regardless of the considered parameter. To find the ratio of the rates of changes of the surface area and circumference, divide:

\(\displaystyle 8\pi r \frac{dr}{dt}=(\phi)2\pi \frac{dr}{dt}\)

\(\displaystyle \phi =4r\)

\(\displaystyle \phi =52\)

Example Question #2122 : Functions

A cube is growing in size. What is the ratio of the rate of growth of the cube's volume to the rate of growth of its surface area when its sides have length 16?

Possible Answers:

\(\displaystyle 2\)

\(\displaystyle 4\)

\(\displaystyle 32\)

\(\displaystyle 16\)

\(\displaystyle 8\)

Correct answer:

\(\displaystyle 4\)

Explanation:

Begin by writing the equations for a cube's dimensions. Namely its volume and surface area in terms of the length of its sides:

\(\displaystyle V=s^3\)

\(\displaystyle A=6s^2\)

The rates of change of these can be found by taking the derivative of each side of the equations with respect to time:

\(\displaystyle \frac{dV}{dt}=3s^2\frac{ds}{dt}\)

\(\displaystyle \frac{dA}{dt}=12s\frac{ds}{dt}\)

Now, knowing the length of the sides, simply divide to find the ratio between the rate of change of the volume and surface area:

\(\displaystyle 3s^2\frac{ds}{dt}=(\phi)12s\frac{ds}{dt}\)

\(\displaystyle \phi=\frac{s}{4}\)

\(\displaystyle \phi =4\)

Example Question #242 : Rate Of Change

A cube is diminishing in size. What is the ratio of the rate of loss of the cube's volume to the rate of loss of its surface area when its sides have length 2?

Possible Answers:

\(\displaystyle 4\)

\(\displaystyle \frac{1}{2}\)

\(\displaystyle 2\)

\(\displaystyle \frac{1}{8}\)

\(\displaystyle \frac{1}{4}\)

Correct answer:

\(\displaystyle \frac{1}{2}\)

Explanation:

Begin by writing the equations for a cube's dimensions. Namely its volume and surface area in terms of the length of its sides:

\(\displaystyle V=s^3\)

\(\displaystyle A=6s^2\)

The rates of change of these can be found by taking the derivative of each side of the equations with respect to time:

\(\displaystyle \frac{dV}{dt}=3s^2\frac{ds}{dt}\)

\(\displaystyle \frac{dA}{dt}=12s\frac{ds}{dt}\)

Now, knowing the length of the sides, simply divide to find the ratio between the rate of change of the volume and surface area:

\(\displaystyle 3s^2\frac{ds}{dt}=(\phi)12s\frac{ds}{dt}\)

\(\displaystyle \phi=\frac{s}{4}\)

\(\displaystyle \phi =\frac{1}{2}\)

Example Question #243 : Rate Of Change

A cube is growing in size. What is the ratio of the rate of growth of the cube's volume to the rate of growth of its diagonal when its sides have length 1?

Possible Answers:

\(\displaystyle 2\sqrt{3}\)

\(\displaystyle \sqrt{3}\)

\(\displaystyle 3\)

\(\displaystyle \frac{\sqrt{3}}{3}\)

\(\displaystyle \frac{1}{3}\)

Correct answer:

\(\displaystyle \sqrt{3}\)

Explanation:

Begin by writing the equations for a cube's dimensions. Namely its volume and diagonal in terms of the length of its sides:

\(\displaystyle V=s^3\)

\(\displaystyle d=s\sqrt{3}\)

The rates of change of these can be found by taking the derivative of each side of the equations with respect to time:

\(\displaystyle \frac{dV}{dt}=3s^2\frac{ds}{dt}\)

\(\displaystyle \frac{dd}{dt}=\sqrt{3}\frac{ds}{dt}\)

Now, knowing the length of the sides, simply divide to find the ratio between the rate of change of the volume and diagonal:

\(\displaystyle 3s^2\frac{ds}{dt}=(\phi)\sqrt{3}\frac{ds}{dt}\)

\(\displaystyle \phi=s^2\sqrt{3}\)

\(\displaystyle \phi =\sqrt{3}\)

Example Question #244 : Rate Of Change

A cube is diminishing in size. What is the ratio of the rate of loss of the cube's volume to the rate of loss of its diagonal when its sides have length 3?

Possible Answers:

\(\displaystyle \frac{\sqrt{3}}{3}\)

\(\displaystyle \frac{\sqrt{3}}{9}\)

\(\displaystyle \sqrt{3}\)

\(\displaystyle 3\sqrt{3}\)

\(\displaystyle 9\sqrt{3}\)

Correct answer:

\(\displaystyle 9\sqrt{3}\)

Explanation:

Begin by writing the equations for a cube's dimensions. Namely its volume and diagonal in terms of the length of its sides:

\(\displaystyle V=s^3\)

\(\displaystyle d=s\sqrt{3}\)

The rates of change of these can be found by taking the derivative of each side of the equations with respect to time:

\(\displaystyle \frac{dV}{dt}=3s^2\frac{ds}{dt}\)

\(\displaystyle \frac{dd}{dt}=\sqrt{3}\frac{ds}{dt}\)

Now, knowing the length of the sides, simply divide to find the ratio between the rate of change of the volume and diagonal:

\(\displaystyle 3s^2\frac{ds}{dt}=(\phi)\sqrt{3}\frac{ds}{dt}\)

\(\displaystyle \phi=s^2\sqrt{3}\)

\(\displaystyle \phi =9\sqrt{3}\)

Example Question #245 : Rate Of Change

A cube is growing in size. What is the ratio of the rate of growth of the cube's surface area to the rate of growth of its diagonal when its sides have length 5?

Possible Answers:

\(\displaystyle 25\sqrt{3}\)

\(\displaystyle 4\sqrt{3}\)

\(\displaystyle 5\sqrt{3}\)

\(\displaystyle 20\sqrt{3}\)

\(\displaystyle 10\sqrt{3}\)

Correct answer:

\(\displaystyle 20\sqrt{3}\)

Explanation:

Begin by writing the equations for a cube's dimensions. Namely its surface area and diagonal in terms of the length of its sides:

\(\displaystyle A=6s^2\)

\(\displaystyle d=s\sqrt{3}\)

The rates of change of these can be found by taking the derivative of each side of the equations with respect to time:

\(\displaystyle \frac{dA}{dt}=12s\frac{ds}{dt}\)

\(\displaystyle \frac{dd}{dt}=\sqrt{3}\frac{ds}{dt}\)

Now, knowing the length of the sides, simply divide to find the ratio between the rate of change of the surface area and diagonal:

\(\displaystyle 12s\frac{ds}{dt}=(\phi)\sqrt{3}\frac{ds}{dt}\)

\(\displaystyle \phi=4s\sqrt{3}\)

\(\displaystyle \phi =20\sqrt{3}\)

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