1. The problem statement, all variables and given/known data A driver carelessly ignores the reduced speed limit of 40.0 km/h in a school zone and continues at 65 km/h. Assuming a good reaction time of 0.80 s, how many more metres will it take him to stop than if he had reduced his speed? Assume 2000kg car has a constant braking friction of 12000N. (Must use work-energy theorem) va=11.11m/s vb=18.05ms Ff=12000N m=2000kg g=9.8m/s^2 2. Relevant equations Ff=μFn Work done to an object = change in kinetic energy Wf=Ek μmgd=1/2mv^2 d=v^2/2μg 3. The attempt at a solution μ=Ff/Fn μ=12000N/(2000kg*9.8m/s^2) μ=0.61 da=(11.11m/s)^2/2*(0.61)(9.8m/s^2) da=10.32m db=(18.05m/s)^2/2*(0.61)(9.8m.s^2) db=27.25m Δd=db-da Δd=27.25m - 10.32m Δd=16.93 Therefore it takes the driver 16.93m longer to stop than if he slowed his speed.