Use Green's theorem to find the work done by the force F(x,y)=x(x+y)+x2) in moving a particle from the origin along the x-axis to (5,0), then along the line segment to (0,5), and then back to the origin along the y-axis.
Q. Use Green's theorem to find the work done by the force F(x,y)=x(x+y)+x2) in moving a particle from the origin along the x-axis to (5,0), then along the line segment to (0,5), and then back to the origin along the y-axis.
Set up problem using Green's theorem: Understand and set up the problem using Green's theorem. Green's theorem relates a line integral around a simple closed curve C and a double integral over the plane region D bounded by C. We need to convert the force field into a form suitable for applying Green's theorem. F(x,y)=x(x+y)+x2 can be rewritten as P(x,y)=x(x+y) and Q(x,y)=x2.
Apply Green's theorem: Apply Green's theorem. Green's theorem states that the line integral of F around C is equal to the double integral over D of (∂x∂Q−∂y∂P)dA. Calculate ∂x∂Q and ∂y∂P: ∂x∂Q=2x, ∂y∂P=x. So, ∂x∂Q−∂y∂P=2x−x=x.
Set up double integral: Set up the double integral. The region D is a right triangle with vertices at (0,0), (5,0), and (0,5). The limits of integration are from x=0 to x=5 and for each x, y goes from 0 to 5−x. Set up the integral: (0,0)0.
Calculate double integral: Calculate the double integral.First, integrate with respect to y:∫y=05−xxdy=x[y]05−x=x(5−x).Now, integrate with respect to x:∫x=05x(5−x)dx=∫x=05(5x−x2)dx.
Finish calculation: Finish the calculation.Calculate ∫x=05(5x−x2)dx:= [25x2−3x3] from 0 to 5= (5⋅225−3125)= (2125−3125)= (6375−6250)= \frac{125}{6}.