As part of a safety investigation, two 1400 {\rm kg} cars traveling at 23 {\rm m/s} are crashed into different barriers.

As part of a safety investigation, two 1400 {rm kg} cars traveling at 23 {rm m/s} are crashed into different barriers. Find the average forces exerted on (a) the car that hits a line of water barrels and takes 1.7 {rm s} to stop, and (b) the car that hits a concrete barrier and takes 0.4 {rm s} to stop.