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

In summary, The snowball's radius is changing at a rate of 2 cm/min while rolling down a hill. When the radius is 8 cm, the rate of change of the surface area is 32pi. However, this formula is only applicable if we are considering the snowball as a disk. If we are considering the snowball as a sphere, the correct formula to use would be the surface area of a sphere, 4pi*r^2. It is important to include units in the answer.
  • #1
hunter55
3
0

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
 
Physics news on Phys.org
  • #2
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.
 
  • #3
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.)
 

1. What is the formula for finding the related rate of change of the radius?

The formula for finding the related rate of change of the radius is given by dR/dt = (dA/dt)/(2πR), where R is the radius and A is the area of the circle.

2. How is the related rate of change of the radius related to the related rate of change of the area of a circle?

The related rate of change of the radius is directly proportional to the related rate of change of the area of a circle. This means that as the radius changes, the area changes at a proportional rate.

3. Can the related rate of change of the radius be negative?

Yes, the related rate of change of the radius can be negative. This would indicate that the radius is decreasing over time, resulting in a decrease in the area of the circle.

4. How are the related rates of two circles with different radii related?

The related rates of two circles with different radii are not directly related. The rate of change of the radius depends on the specific circle, and the relationship between the two circles would depend on their individual radii and rates of change.

5. How can the related rate of change of the radius be used in real-world applications?

The related rate of change of the radius can be used in various real-world applications, such as calculating the rate of change of the area of a growing or shrinking circular object, or in determining the speed of an object moving in a circular path. It is also used in fields such as engineering and physics to analyze and solve problems involving circular motion and related rates.

Similar threads

  • Calculus and Beyond Homework Help
Replies
33
Views
2K
  • Calculus and Beyond Homework Help
Replies
6
Views
2K
  • Calculus and Beyond Homework Help
Replies
4
Views
2K
  • Calculus and Beyond Homework Help
Replies
13
Views
1K
  • Calculus and Beyond Homework Help
Replies
3
Views
2K
  • Calculus and Beyond Homework Help
Replies
30
Views
3K
  • Calculus and Beyond Homework Help
Replies
4
Views
2K
Replies
5
Views
2K
  • Calculus and Beyond Homework Help
Replies
8
Views
1K
  • Calculus and Beyond Homework Help
Replies
4
Views
1K
Back
Top