## The position vector **r** describes the path of an object moving in the xy-plane. ### **Position Vector** [ r(t) = t^2 \mathbf{i} + t \mathbf{j} ] ### **Point** [ (4,, 2) ] --- ### **(a)** Find the velocity vector (v(t)), speed (s(t)), and acceleration vector (a(t)) of the object. [ v(t) = \langle 2t,\ 1 \rangle ] [ s(t) = \sqrt{4t^2 + 1} ] [ a(t) = \langle 2,\ 0 \rangle ] --- ### **(b)** Evaluate the velocity vector and acceleration vector of the object at the given point. [ v(2) = \langle 4,\ 1 \rangle ] [ a(2) = \langle 2,\ 0 \rangle ] 1.讲解题目是什意思? 2.讲解解题过程