Math Problem Statement

The radius of a right circular cylinder is given by

t + 8 and its height is 1 8

t , where t is time in seconds and the dimensions are in inches. Find the rate of change of the volume with respect to time (in in3/sec).

Solution

The volume VV of a right circular cylinder is given by the formula:

V=πr2hV = \pi r^2 h

where rr is the radius and hh is the height of the cylinder.

Step 1: Express the radius and height in terms of time tt

  • Radius r=t+8r = t + 8
  • Height h=18th = \frac{1}{8}t

Step 2: Substitute the radius and height into the volume formula

V=π(t+8)2(18t)V = \pi (t + 8)^2 \left( \frac{1}{8}t \right)

Step 3: Simplify the volume expression

V=π8t(t+8)2V = \frac{\pi}{8} t (t + 8)^2

Step 4: Differentiate the volume with respect to time tt

We will use the product rule and chain rule to differentiate:

  1. First, let u=(t+8)2u = (t + 8)^2, so the derivative of uu is: ddt(t+8)2=2(t+8)\frac{d}{dt} (t + 8)^2 = 2(t + 8)

  2. Now apply the product rule to V=π8t(t+8)2V = \frac{\pi}{8} t (t + 8)^2: dVdt=π8[(t+8)2+t2(t+8)]\frac{dV}{dt} = \frac{\pi}{8} \left[ (t + 8)^2 + t \cdot 2(t + 8) \right]

Step 5: Simplify the derivative

dVdt=π8[(t+8)2+2t(t+8)]\frac{dV}{dt} = \frac{\pi}{8} \left[ (t + 8)^2 + 2t(t + 8) \right] dVdt=π8[(t+8)(t+8)+2t(t+8)]\frac{dV}{dt} = \frac{\pi}{8} \left[ (t + 8)(t + 8) + 2t(t + 8) \right] dVdt=π8[(t+8)(t+8+2t)]\frac{dV}{dt} = \frac{\pi}{8} \left[ (t + 8)(t + 8 + 2t) \right] dVdt=π8(t+8)(3t+8)\frac{dV}{dt} = \frac{\pi}{8} (t + 8)(3t + 8)

Final Answer:

The rate of change of the volume with respect to time is: dVdt=π8(t+8)(3t+8) in3/sec\frac{dV}{dt} = \frac{\pi}{8} (t + 8)(3t + 8) \ \text{in}^3/\text{sec}

Would you like further details on any of these steps?


Here are 5 related questions to expand on this:

  1. How does the rate of change of volume behave as time tt increases?
  2. What happens to the volume if the height or radius were constant instead of changing with time?
  3. Can we find the rate of change of surface area of this cylinder with respect to time?
  4. How do changes in radius and height affect the instantaneous volume growth?
  5. What is the volume at t=0t = 0 and how does it change at t=1t = 1?

Tip: When dealing with composite functions like this, always apply the chain rule and product rule carefully during differentiation.

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Math Problem Analysis

Mathematical Concepts

Calculus
Differentiation
Product Rule
Chain Rule
Geometry

Formulas

Volume of a cylinder: V = πr^2h
Product rule: d(uv)/dt = u'v + uv'
Chain rule

Theorems

Product rule for differentiation
Chain rule for composite functions

Suitable Grade Level

Grades 11-12 or College Level