Exam 10: Vector Functions

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A particle is moving along the curve described by the parametric equations x=5t,y=2t3,z=35t5x = 5 t , y = 2 t ^ { 3 } , z = \frac { 3 } { 5 } t ^ { 5 } . Determine the velocity and acceleration vectors as well as the speed of the particle when t = 3.

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v(3)=5i+54j+243k;a(3)=36j+324k;v(3)=61,990\mathbf { v } ( 3 ) = 5 \mathbf { i } + 54 \mathbf { j } + 243 \mathbf { k } ; \mathbf { a } ( 3 ) = 36 \mathbf { j } + 324 \mathbf { k } ; | \mathbf { v } ( 3 ) | = \sqrt { 61,990 }

Let r(t)=cos2ti+2tj+sin2tk\mathbf { r } ( t ) = \cos 2 t \mathbf { i } + 2 t \mathbf { j } + \sin 2 t \mathbf { k } . Show that the acceleration vector is parallel to the normal vector N(t).

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v(t)=v(t)=4(cos22t+sin22t)+2=6, so aT=v(t)=0 and thus a(t)=aN N is parallel to Nv ( t ) = | \mathbf { v } ( t ) | = \sqrt { 4 \left( \cos ^ { 2 } 2 t + \sin ^ { 2 } 2 t \right) + 2 } = \sqrt { 6 } , \text { so } a _ { T } = v ^ { \prime } ( t ) = 0 \text { and thus } \mathbf { a } ( t ) = a _ { N } \mathrm {~N} \text { is parallel to } \mathbf { N }

Find a parametric representation for the surface consisting of that part of the hyperboloid x2y2+z2=1- x ^ { 2 } - y ^ { 2 } + z ^ { 2 } = 1 that lies below the rectangle [1,1]×[3,3][ - 1,1 ] \times [ - 3,3 ] .

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x=xx = x , y=yy = y , z=1+x2+y2z = - \sqrt { 1 + x ^ { 2 } + y ^ { 2 } } where 1x1- 1 \leq x \leq 1 and 3y3- 3 \leq y \leq 3

Find the length of the circular helix described by x=2cost,y=2sint,z=5t,0t2πx = 2 \cos t , y = 2 \sin t , z = \sqrt { 5 } t , 0 \leq t \leq 2 \pi

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Find the equation of the osculating circle of the curve y=ex at x=0y = e ^ { x } \text { at } x = 0

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The position of a particle at time t is given parametrically by y = t2 and x = 13\frac { 1 } { 3 } (t3 - 3t). Show that the particle crosses the y-axis three times.

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Use the curvature formula to compute the curvature of a straight line y = mx + b.

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Let the acceleration of a particle be a(t)=i+k\mathbf { a } ( t ) = \mathbf { i } + \mathbf { k } , and let its velocity when t = 0 be v(0)=j\mathbf { v } ( 0 ) = \mathbf { j } . Find its velocity when t = 1.

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Find the tangent vector r\mathbf { r } ^ { \prime } (t) of the function r (t) = sin 2t i - cos 2t j when t = π6\frac { \pi } { 6 } .

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Identify the geometric object that is represented by parametric equations r(t)=3cost,3sint,t\mathbf { r } ( t ) = \langle 3 \cos t , 3 \sin t , t \rangle .

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Find the curvature KK of the curve r(t)=(t,t,1t2)\mathbf { r } ( t ) = \left( t , t , 1 - t ^ { 2 } \right) at t = 0.

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Find the curvature KK of the curve r(t)=sin2t,3t,cos2t when t=π2\mathbf { r } ( t ) = \langle \sin 2 t , 3 t , \cos 2 t \rangle \text { when } t = \frac { \pi } { 2 }

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Find an expression for ddt[(u(t)×v(t))w(t)]\frac { d } { d t } [ ( \mathbf { u } ( t ) \times \mathbf { v } ( t ) ) \cdot \mathbf { w } ( t ) ]

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Consider y=sinx,π<x<πy = \sin x , - \pi < x < \pi . Determine graphically where the curvature is maximal and minimal.

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Suppose a particle moves in the plane according to the vector-valued function r(t)=2eti+etj\mathbf { r } ( t ) = 2 e ^ { t } \mathbf { i } + e ^ { - t } \mathbf { j } , where t represents time. Find v(t),v(t), and a(t)\mathbf { v } ( t ) , | \mathbf { v } ( t ) | , \text { and } \mathbf { a } ( t ) , and sketch a graph showing the path taken by the particle indicating the direction of motion.  Suppose a particle moves in the plane according to the vector-valued function  \mathbf { r } ( t ) = 2 e ^ { t } \mathbf { i } + e ^ { - t } \mathbf { j }  , where t represents time. Find  \mathbf { v } ( t ) , | \mathbf { v } ( t ) | , \text { and } \mathbf { a } ( t )  , and sketch a graph showing the path taken by the particle indicating the direction of motion.

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Where does the tangent line to the curve r(t)=e2t,cost,3sint\mathbf { r } ( t ) = \left\langle e ^ { - 2 t } , \cos t , 3 \sin t \right\rangle at (1,1,0) intersect the yz-plane?

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Find the derivative of the vector function r (t) = t i + sin t j when t = 0.

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Find a parametric representation for the surface consisting of that part of the cylinder x2+z2=1x ^ { 2 } + z ^ { 2 } = 1 that lies between the planes y=1y = - 1 and y = 3.

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Find the domain of vector function r=1t,lnt,e2t\mathbf { r } = \left\langle \sqrt { 1 - t } , \ln t , e ^ { 2 t } \right\rangle

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Find the unit normal vector N(t) to the curve r (t) = t,2t,t2\left\langle t , 2 t , t ^ { 2 } \right\rangle when t = 1.

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