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Ch. 3 - Derivatives
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Not the one you use?Change textbook
Chapter 3, Problem 3.11.7a

The volume V of a sphere of radius r changes over time t.
a. Find an equation relating dV/dt to dr/dt.

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1
Start with the formula for the volume of a sphere: V = (4/3)πr^3.
Differentiate both sides of the equation with respect to time t to find the rate of change of volume with respect to time, dV/dt.
Apply the chain rule to differentiate the right side: dV/dt = d/dt[(4/3)πr^3] = (4/3)π * 3r^2 * (dr/dt).
Simplify the expression: dV/dt = 4πr^2 * (dr/dt).
This equation shows that the rate of change of the volume of the sphere with respect to time, dV/dt, is related to the rate of change of the radius with respect to time, dr/dt, by the factor 4πr^2.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Related Rates

Related rates involve finding the rate at which one quantity changes in relation to another. In this context, we are interested in how the volume of a sphere changes with respect to time as the radius changes. By applying the chain rule, we can relate the rates of change of volume and radius.
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Volume of a Sphere

The volume V of a sphere is given by the formula V = (4/3)πr³, where r is the radius. This formula is essential for deriving the relationship between the volume and the radius. Understanding how volume depends on radius is crucial for applying calculus to find the rate of change of volume with respect to time.
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Chain Rule

The chain rule is a fundamental principle in calculus used to differentiate composite functions. In this problem, we apply the chain rule to express dV/dt in terms of dr/dt. This allows us to find how the volume's rate of change is influenced by the radius's rate of change, linking the two quantities effectively.
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Intro to the Chain Rule