Chapter 12: Vectors and the Geometry of Space - Section 12.2 - Vectors - Exercises 12.2 - Page 704: 27

$5k$

Formula to find the unit vector $\hat{\textbf{v}}$ is: $\hat{\textbf{v}}=\dfrac{v}{|v|}$ Given:$v=0i+0j+5k$ $|v|=\sqrt{0^2+(0)^2+(5)^2}=\sqrt {25}=5$ Thus, $\hat{\textbf{v}}=\dfrac{0i+0j+5k}{5}=(0,0,1)=5k$ and $v=|v|\hat{\textbf{v}}=5(1k)=5k$