## Physics (10th Edition)

a) -39 400 m/s b) -5.78 $\times 10^{-4}$ $m/s^{2}$
a) $\Delta$ v = v - u = -18.5 - 20.9 = -39.4 km/s = -39 400 m/s b) time in seconds = 2.16 years $\times$ 365 days/year $\times$ 24 hours/day $\times$ 60 min/hours $\times$ 60 sec/min $\approx$ 6.81 $\times$ $10^{7}$ seconds a = $\frac{\Delta v}{t}$ = $\frac{-39 4000}{68 100 000}$ $\approx$ -5.78 $\times 10^{-4}$ $m/s^{2}$