Chapter 7, Problem 3Q

Is positive or negative work done by a constant force $\stackrel{\to }{F}$ on a particle during a straight-line displacement $\stackrel{\to }{d}$ if (a) the angle between $\stackrel{\to }{F}$ and $\stackrel{\to }{d}$ is 30°; (b) the angle is 100°; (c) $\stackrel{\to }{F}$ = 2 $\hat{i}$− 3 $\hat{j}$ and $\stackrel{\to }{d}$ = −4 $\hat{i}$?