A car is travelling 20m/s along a straight road. The driver sees a 36km/h speed limit sign 100m ahead. What constant retardation is required to reduce the speed to 36km/h in this distance. Find also the time taken by the car to reach the speed limit region.

Answer 1

vf^2=vi^2 + 2ad where a=force/mass

solve for a, then

time=changevelocity/a