Math Problem Statement

Let the curve C be the line segment from (2, -1, 3) to (5, 1, 5) and let F(x, y, z) = <-y, z, x> be a force field. Calculate the work done by F to move a particle along the curve C.

Solution

This problem asks us to calculate the work done by the force field F(x,y,z)=y,z,x\mathbf{F}(x, y, z) = \langle -y, z, x \rangle in moving a particle along the curve C\mathbf{C}, which is the line segment from (2,1,3)(2, -1, 3) to (5,1,5)(5, 1, 5).

Step-by-step solution:

  1. Parameterize the curve C\mathbf{C}: The curve C\mathbf{C} is a line segment, so we can parameterize it as: r(t)=(1t)r0+tr1,\mathbf{r}(t) = (1-t)\mathbf{r}_0 + t\mathbf{r}_1, where r0=(2,1,3)\mathbf{r}_0 = (2, -1, 3) and r1=(5,1,5)\mathbf{r}_1 = (5, 1, 5), and t[0,1]t \in [0, 1].

    Simplifying: r(t)=2+3t,1+2t,3+2t.\mathbf{r}(t) = \langle 2 + 3t, -1 + 2t, 3 + 2t \rangle.

  2. Find r(t)\mathbf{r}'(t): Differentiate r(t)\mathbf{r}(t) with respect to tt: r(t)=3,2,2.\mathbf{r}'(t) = \langle 3, 2, 2 \rangle.

  3. Substitute r(t)\mathbf{r}(t) into F\mathbf{F}: The force field at r(t)\mathbf{r}(t) is: F(r(t))=y,z,x=(1+2t),3+2t,2+3t.\mathbf{F}(\mathbf{r}(t)) = \langle -y, z, x \rangle = \langle -(-1 + 2t), 3 + 2t, 2 + 3t \rangle. Simplify: F(r(t))=12t,3+2t,2+3t.\mathbf{F}(\mathbf{r}(t)) = \langle 1 - 2t, 3 + 2t, 2 + 3t \rangle.

  4. Calculate the work: The work done is given by: W=CFdr,W = \int_C \mathbf{F} \cdot d\mathbf{r}, which becomes: W=01F(r(t))r(t)dt.W = \int_0^1 \mathbf{F}(\mathbf{r}(t)) \cdot \mathbf{r}'(t) \, dt.

    Substitute F(r(t))=12t,3+2t,2+3t\mathbf{F}(\mathbf{r}(t)) = \langle 1 - 2t, 3 + 2t, 2 + 3t \rangle and r(t)=3,2,2\mathbf{r}'(t) = \langle 3, 2, 2 \rangle: W=0112t,3+2t,2+3t3,2,2dt.W = \int_0^1 \langle 1 - 2t, 3 + 2t, 2 + 3t \rangle \cdot \langle 3, 2, 2 \rangle \, dt.

    Compute the dot product: F(r(t))r(t)=(12t)(3)+(3+2t)(2)+(2+3t)(2).\mathbf{F}(\mathbf{r}(t)) \cdot \mathbf{r}'(t) = (1 - 2t)(3) + (3 + 2t)(2) + (2 + 3t)(2). Simplify: F(r(t))r(t)=36t+6+4t+4+6t.\mathbf{F}(\mathbf{r}(t)) \cdot \mathbf{r}'(t) = 3 - 6t + 6 + 4t + 4 + 6t. Combine terms: F(r(t))r(t)=13+4t.\mathbf{F}(\mathbf{r}(t)) \cdot \mathbf{r}'(t) = 13 + 4t.

  5. Integrate: Now, integrate 13+4t13 + 4t from t=0t = 0 to t=1t = 1: W=01(13+4t)dt.W = \int_0^1 (13 + 4t) \, dt. Compute: W=[13t+2t2]01.W = \left[ 13t + 2t^2 \right]_0^1. Evaluate: W=13(1)+2(1)2(13(0)+2(0)2).W = 13(1) + 2(1)^2 - (13(0) + 2(0)^2). Simplify: W=13+2=15.W = 13 + 2 = 15.

Final Answer:

The work done by the force field F\mathbf{F} along the curve C\mathbf{C} is: 15\boxed{15}

Let me know if you'd like additional details or clarifications!


Related Questions:

  1. How is a force field like F\mathbf{F} used in real-world applications?
  2. What are other parameterization techniques for more complex curves?
  3. What is the physical significance of the work done by a force field?
  4. How would the calculation change if the curve C\mathbf{C} were not a straight line?
  5. What are conservative vector fields, and how do they simplify work calculations?

Tip:

Always check if the force field is conservative. If it is, calculating work becomes easier using potential functions!

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Math Problem Analysis

Mathematical Concepts

Vector Calculus
Work in Physics
Line Integrals

Formulas

Work W = ∫C F ⋅ dr
Parametric representation of a line segment

Theorems

Line integral of a vector field
Dot product properties

Suitable Grade Level

Undergraduate (Calculus II/III)