Chapter 7 - Kinetic Energy and Work - Problems - Page 171: 8

$W=4950J$

Note that the formula for work is defined as $$W=\vec{F} ·\vec{d}$$ Substituting known vectors of $\vec{F}=(210N)\vec{i}-(150N)\vec{j}$ and $\vec{d}=(15m)\vec{i}-(12m)\vec{j}$ yields $$W=[(210N)\vec{i}-(150N)\vec{j}]·[(15m)\vec{i}-(12m)\vec{j}]$$ Remember that $$\vec{u}·\vec{v}=u_1v_1+u_2v_2$$ The dot product is equal to $$W=(210N)(15m)+(-12m)(-150N)$$ $$W=4950J$$