Chapter 12: Vectors and the Geometry of Space - Section 12.3 - The Dot Product - Exercises 12.3 - Page 713: 41

$5\ J$

The work done by a constant force ${\bf F}$ acting through a displacement ${\bf D}=\vec{PQ}$ is ${\bf W}={\bf F}\cdot{\bf D}$ --- ${\bf F}=\langle 5\ N,0\ N\rangle,\qquad {\bf D}=\langle 1\ m,1\ m\rangle$ ${\bf W}=(5N)(1m)+(0N)(1m)=5\ Nm=5\ J$