Multivariable Calculus · free preview

Work and Vector Line Integrals

The vector line integral as accumulated tangential push, computing work of force fields along parametrized paths, and circulation around closed curves.

1. A field pushes a particle along a curve

A field pushes a particle along a curve

2. Two worked computations

Two worked computations

3. Orientation and path language

Orientation and path language

4. Other readings of the same integral

Other readings of the same integral

5. Setting up a work integral

To compute the work of F=(y,x)\mathbf{F} = (y, x) along r(t)=(t,t)\mathbf{r}(t) = (t, t), 0≤t≤10 \le t \le 1, what is the integrand?

6. Swirl versus radial circulation

Around the unit circle counterclockwise, which field has circulation 2π2\pi?

7. Orientation reversal

The circulation of F\mathbf{F} around a closed curve counterclockwise is 55. What is the circulation clockwise?

8. Work along a segment

For F=(y,x)\mathbf{F} = (y, x) along the straight path from (0,0)(0,0) to (1,1)(1,1), the work is ∫012t dt\int_0^1 2t\, dt. Give the value, as a plain number.

9. Voltage along a path

A field's line integral along a path from A to B is 1212. Give the integral along the reversed path from B to A, as a plain integer like -5.

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