Math Problem Statement

The circumference of a sphere was measured to be 84.000 cm with a possible error of 0.50000 cm. Use linear approximation to estimate the maximum error in the calculated surface area and the relative error.

Solution

We are asked to find the maximum error and the relative error in the calculated surface area of a sphere using linear approximation. Here's how we can approach the problem:

Step 1: Formulas Involved

  1. Circumference of a sphere: C=2πrC = 2\pi r, where rr is the radius.

  2. Surface area of a sphere: A=4πr2A = 4\pi r^2.

    We are given the circumference C=84.000cmC = 84.000 \, \text{cm}, and we know there is an error in the circumference measurement of ΔC=0.50000cm\Delta C = 0.50000 \, \text{cm}. We need to find the corresponding maximum error in the surface area using linear approximation.

Step 2: Radius from the Circumference

From the circumference formula C=2πrC = 2\pi r, we can solve for the radius: r=C2π=84.0002π13.37cmr = \frac{C}{2\pi} = \frac{84.000}{2\pi} \approx 13.37 \, \text{cm}

Step 3: Error in Surface Area

Using linear approximation, the differential of the surface area is: dA=dAdrdrdA = \frac{dA}{dr} \cdot dr The derivative of the surface area A=4πr2A = 4\pi r^2 with respect to rr is: dAdr=8πr\frac{dA}{dr} = 8\pi r Thus, the change in surface area dAdA due to a small change drdr in the radius is: dA=8πrdrdA = 8\pi r \cdot dr Now, drdr can be found using the error in the circumference. Since C=2πrC = 2\pi r, the error in rr is: Δr=ΔC2π=0.500002π0.0796cm\Delta r = \frac{\Delta C}{2\pi} = \frac{0.50000}{2\pi} \approx 0.0796 \, \text{cm}

Step 4: Maximum Error in Surface Area

Substitute the values of rr and Δr\Delta r into the expression for dAdA: ΔA=8πrΔr=8π×13.37×0.079633.56cm2\Delta A = 8\pi r \cdot \Delta r = 8\pi \times 13.37 \times 0.0796 \approx 33.56 \, \text{cm}^2

Thus, the maximum error in the calculated surface area is approximately ΔA33.56cm2\Delta A \approx 33.56 \, \text{cm}^2.

Step 5: Relative Error in Surface Area

The relative error in surface area is given by: Relative error=ΔAA\text{Relative error} = \frac{\Delta A}{A} First, we calculate the surface area AA using the radius r=13.37cmr = 13.37 \, \text{cm}: A=4πr2=4π×(13.37)22246.5cm2A = 4\pi r^2 = 4\pi \times (13.37)^2 \approx 2246.5 \, \text{cm}^2 Now, the relative error is: Relative error=33.562246.50.01494(or 1.494%)\text{Relative error} = \frac{33.56}{2246.5} \approx 0.01494 \, (\text{or } 1.494\%)

Final Answers:

  • Maximum error in the calculated surface area: 33.56cm2\approx 33.56 \, \text{cm}^2
  • Relative error in the calculated surface area: 0.01494\approx 0.01494 or 1.494%1.494\%

Would you like further details or have any questions?

Here are 5 related questions to explore:

  1. How is linear approximation applied in other physical problems?
  2. What is the difference between absolute and relative error?
  3. Can we apply a similar process to estimate the error in the volume of the sphere?
  4. How would a larger error in the circumference affect the error in surface area?
  5. Why is the relative error often a more useful measure than the absolute error?

Tip: When dealing with measurement errors, always remember to distinguish between absolute and relative errors, as they provide different insights into the impact of uncertainties.

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Math Problem Analysis

Mathematical Concepts

Linear Approximation
Error Propagation
Surface Area of Sphere

Formulas

Circumference: C = 2πr
Surface Area: A = 4πr^2
Error in Surface Area: dA = 8πr dr

Theorems

Differentiation of Surface Area with respect to Radius

Suitable Grade Level

College Level (Calculus)