Green's theorem - area of a cycloid

The correct answer is 8pi.In summary, when using Green's Theorem to find the area of a region, the choice of force field does not matter. However, it is important to be careful when calculating integrals to ensure the correct answer is obtained.
  • #1
Feodalherren
605
6

Homework Statement



Use Green’s Theorem to find the area of the region between the x – axis and one arch of the cycloid
parameterized by p(t) = < t-2sin(t),2-2cos(t)> for 0≤t≤2∏
p

Homework Equations


The Attempt at a Solution


My problem here is that I get different answers depending on if I use
F=<0,x> or F = <-y,0>

The 8∏ answer that I have to the right is the correct one. How do I know which force field to pick?

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  • #2
Feodalherren said:

Homework Statement



Use Green’s Theorem to find the area of the region between the x – axis and one arch of the cycloid
parameterized by p(t) = < t-2sin(t),2-2cos(t)> for 0≤t≤2∏
p

Homework Equations





The Attempt at a Solution


My problem here is that I get different answers depending on if I use
F=<0,x> or F = <-y,0>

The 8∏ answer that I have to the right is the correct one. How do I know which force field to pick?

You can pick either one. The only problem is that you did the first integral wrong. The integral of t*sin(t) between 0 and 2pi isn't zero.
 

1. What is Green's theorem and how is it related to finding the area of a cycloid?

Green's theorem is a mathematical tool used to calculate the area of a region in a plane. It is based on the fundamental theorem of calculus and states that the line integral of a two-dimensional vector field around a closed curve is equal to the double integral of the curl of the vector field over the region enclosed by the curve. This theorem can be applied to the area of a cycloid by considering the curve as the boundary of the region and the vector field as the velocity of a point moving along the curve.

2. How is the cycloid curve defined and why is it important in Green's theorem?

The cycloid curve is defined as the path traced by a point on a circle as the circle rolls along a straight line. It is important in Green's theorem because it is a special case of a parametric curve with a well-defined velocity vector, making it ideal for applying the theorem to calculate its area.

3. Can Green's theorem be used to find the area of any curve?

No, Green's theorem can only be used to find the area of a curve if the curve is a closed curve and can be defined as the boundary of a region in the plane. Additionally, the curve must have a well-defined velocity vector that is continuous and has a continuous first derivative.

4. Are there any limitations to using Green's theorem to find the area of a cycloid?

Yes, there are some limitations to using Green's theorem for calculating the area of a cycloid. Since the theorem requires the curve to have a continuous first derivative, it cannot be applied to cycloids with cusps or self-intersections. Additionally, the theorem assumes that the curve is simple, meaning it does not intersect itself or have any holes in the region it encloses.

5. Are there any practical applications of Green's theorem and the area of a cycloid?

Yes, Green's theorem and the area of a cycloid have practical applications in physics and engineering, particularly in the study of motion and fluid dynamics. For example, they can be used to calculate the work done by a force on a moving object or the circulation of a fluid around a closed path. The cycloid curve is also commonly seen in the design of gears, pendulums, and other mechanical systems.

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