6. A car traveling 64 km/hr (40 mi/h) brakes suddenly to avoid a dog crossing the road. It accelerated at a rate of -1350 mi/h2. What was its speed after 0.5 min?
vf=vi+at
change that acceleration to m/s^2
-1350mi/hr^2 (1hr/3600sec)^2*1609m/mi
=-.167m/s^2 check that.