Explanation

(b) $\overrightarrow{\mathbf{v}} = 6\widehat{\mathbf{i}} - 8\widehat{\mathbf{j}}$
Comparing with
$\overrightarrow{\mathbf{v}} = v_{x}\widehat{\mathbf{i}} = v_{y} = \widehat{\mathbf{j}}$, we get
[image:4_image118.emf]
and $u_{x} = 6\ ms^{- 2}$
Also, $u^{2} = v_{x}^{2} + v_{y}^{2}$
36+64=100
or $v = 10ms^{- 1}$
$\sin\theta = \frac{8}{10}$ and $\cos\theta = \frac{6}{10}$
$R = \frac{v^{2}sin2\theta}{g} = \frac{2v^{2}\sin\theta\cos\theta}{g}$
$R = 2 \times 10 \times 10 \times \frac{8}{10} \times \frac{6}{10} \times \frac{1}{10}m = 9.6\ m$