- I-Learn, Class Pictures, Learning Targets, Text Book Practice
- Prep Tasks: Unit 1 - Motion, Unit 2 - Derivatives, Unit 3 - Integration, Unit 4 - Vector Calculus
Prep
We're in Unit 1 - Motion. Your homework assignment each day is to spend 1-2 hours working on the next 4 tasks from the current unit's prep.
Brain Gains (Rapid Recall, Jivin' Generation)

- Set up a work integral that will give the work done by $\vec F(x,y) = (x+y, -x^2)$ on an object that follows the path $\vec r(t) = (t^2, t^3)$ for $t\in [-1,2] $. The work integral is written using any of $$\ds\int_C Mdx+Ndy=\ds\int_C \vec F\cdot d\vec r=\ds\int_{a}^{b}\vec F(\vec r(t))\frac{d\vec r}{dt}dt.$$
Solution
We have the following:
- $M=x+y = t^2+t^3$,
- $N=x^2 = -(t^2)^2$,
- $dx = 2tdt$,
- $dy = 3t^2dt$.
This gives $$\int_C Mdx+Ndy =\int_{-1}^3 \underbrace{(t^2+t^3)}_{M}\underbrace{(2tdt)}_{dx}+\underbrace{(-(t^2)^2)}_{N}\underbrace{(3t^2dt)}_{dy} .$$
We can perform all the computations above with Mathematica, as well as create a plot to visualize what's happening.
ClearAll[F, r, tB, xB, yB]
r[t_] := {t^2, t^3}
tB = {t, -1, 2}
F[x_, y_] := {x + y, -x^2}
F @@ r[t]
dr = r'[t]
dW = (F @@ r[t]) . r'[t]
Integrate[dW, tB]
xB = {x, 0, 4}
yB = {y, -2, 10}
Show[
ParametricPlot[r[t], Evaluate[tB]],
VectorPlot[F[x, y], xB, yB, VectorScaling -> Automatic, VectorStyle -> Automatic]
]
Self Directed Learning Projects
- Have a specific plan that helps you develop deeper understanding related to something from the unit. Think about Bloom's Taxonomy (see 1 and 2), and focus your efforts towards the highest levels.
- Carry out the plan, making modifications as needed (follow new leads, keep in the time constraints, etc.).
- Create something based on what you learned (Bloom's taxonomy).
- Share your work publicly.
- Complete a short steward report to reflect on your learning process.
Group Problems
- A force given by $\vec F = (2y,-x+y)$ acts on an object as it moves along the curve $\vec r(t) =(t^2,3t+1)$ for $-1\leq t\leq 2$. Compute $\ds \int_C\vec F\cdot \frac{d\vec r}{dt}dt$ (the work done by the force along the curve).
- Draw the parametric curve $\vec r(t) = (3\cos t, t/\pi, 4\sin t)$ for $0\leq t\leq 6\pi$.
- If an object follows this parametrization, state the velocity, speed, and acceleration of that object.
- Give a vector equation of the tangent line to the curve above at $t=\pi$.
- Set up an integral that gives the length of this curve. Just set it up.
- At time $t=2\pi$, compute the component of the acceleration that is parallel to the velocity, and the component of the acceleration that is orthogonal to the velocity.
- Let $\vec F = (a,b,c)$ and $\vec d = (x,y,z)$. Compute the component of $\vec F$ that parallel to $\vec d$ and the component of $\vec F$ that is orthogonal to $\vec d$. [Feel free to pick specific values for $a, b, c, x, y, z$, or do this problem symbolically.]
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