Question

A typical automobile under hard braking loses speed at a rate of about 7.1 m/s2; the typical reaction time to engage the brakes is 0.51 s. A local school board sets the speed limit in a school zone such that all cars should be able to stop in 4.2 m.

(a) What maximum speed does this imply for an automobile in this zone? in mi/h

(b) What fraction of the 4.2 m is due to the reaction time?

Answer 1