To evaluate the work done by a vector field F along a curve C, we compute the line integral ∫CF⋅dr.
Step 1: Parameterize the line segment C.
The line segment goes from P0(2,0) to P1(0,2). We can parameterize it as r(t)=(1−t)P0+tP1 for 0≤t≤1.
r(t)=(1−t)⟨2,0⟩+t⟨0,2⟩
r(t)=⟨2(1−t),0⟩+⟨0,2t⟩
r(t)=⟨2−2t,2t⟩
So, x(t)=2−2t and y(t)=2t.
Step 2: Calculate dr.
First, find the derivative of r(t):
r′(t)=⟨dtd(2−2t),dtd(2t)⟩=⟨−2,2⟩
Then, dr=r′(t)dt=⟨−2,2⟩dt.
Step 3: Express the vector field F(x,y) in terms of t.
The given vector field is F(x,y)=⟨y−x,x⟩.
Substitute x=2−2t and y=2t:
F(x(t),y(t))=⟨(2t)−(2−2t),(2−2t)⟩
F(x(t),y(t))=⟨2t−2+2t,2−2t⟩
F(x(t),y(t))=⟨4t−2,2−2t⟩
Step 4: Compute the dot product F⋅dr.
F⋅dr=⟨4t−2,2−2t⟩⋅⟨−2,2⟩dt
F⋅dr=((4t−2)(−2)+(2−2t)(2))dt
F⋅dr=(−8t+4+4−4t)dt
F⋅dr=(−12t+8)dt
Step 5: Evaluate the definite integral.
The work done is ∫CF⋅dr=∫01(−12t+8)dt.
∫01(−12t+8)dt=[−122t2+8t]01
=[−6t2+8t]01
Now, evaluate at the limits of integration:
=(−6(1)2+8(1))−(−6(0)2+8(0))
=(−6+8)−(0)
=2
The work done is 2.
Drop the next question.