Related Rates: Finding the Area Change of a Snowball with Changing Radius

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SUMMARY

The discussion focuses on calculating the rate of change of the surface area of a snowball as its radius changes. The correct formula for the surface area of a sphere is identified as 4πr², not πr², which is applicable for a disk. When the radius is 8 cm and the radius changes at a rate of 2 cm/min, the rate of change of the surface area is calculated using the formula dA/dt = 8π cm²/min. The final answer is confirmed to be 32π cm²/min.

PREREQUISITES
  • Understanding of calculus concepts, specifically related rates.
  • Familiarity with the formula for the surface area of a sphere: 4πr².
  • Knowledge of differentiation techniques in calculus.
  • Ability to apply units correctly in mathematical expressions.
NEXT STEPS
  • Study related rates problems in calculus to strengthen understanding.
  • Learn how to derive the surface area formula for different geometric shapes.
  • Practice applying differentiation to real-world scenarios involving changing dimensions.
  • Explore the implications of unit conversions in calculus problems.
USEFUL FOR

Students studying calculus, particularly those focusing on related rates, as well as educators seeking to clarify concepts related to surface area and differentiation.

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Homework Statement


a snowball is rolling donw a hill, its radius is changing at a rate of 2 cm/min. what is the rate of change of the area, when the radius is 8 cm?


Homework Equations



da/dt= 2pir2dr/dt
dat/dt=2pi(8)(2)
32pi ?
is that right


The Attempt at a Solution



32pi
 
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What formula are you using for A? If you are thinking of the snowball as a disk and A=pi*r^2, then yes, dA/dt=pi*2*r*dr/dt. You might want to put units on your answer.
 
As Dick suggested, you are using the wrong formula (because a snowball is NOT a disk). The "area'' referred to here is the SURFACE area of a sphere.
Surface area of a sphere is [itex]4\pi r^2[/itex].

(And, of course, be sure to put units on your answer.)
 

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