일반물리학 1 — Motion in Two and Three Dimensions: Problem 18

18 A moderate wind accelerates a pebble over a horizontal $xy$ plane with a constant acceleration $\vec{a} = (5.00 \text{ m/s}^2)\hat{i} + (7.00 \text{ m/s}^2)\hat{j}$. At time $t = 0$, the velocity is $(4.00 \text{ m/s})\hat{i}$. What are the (a) magnitude and (b) angle of its velocity when it has been displaced by $10.0 \text{ m}$ parallel to the $x$ axis?