In Problem $3,$ the vector in the $x$ -direction is
4 units long. Vectors 7 and $J$ are unit vectors in the $x$ - and $y$ -directions, respectively. A unit vector is a vector that is one unit long. So the $x$ -component of $\bar{p}$ is the vector $4 \vec{\imath},$ a product of a scalar and a vector. A scalar is a quantity that has only magnitude, not direction. Write the $y$ -component of $x$ in Figure $10-1 b$