Engineers are testing two different crash-safety systems by observing cars brought to rest from an initial speed. In Test 1, a car of mass \(M\) traveling at speed \(v\) is brought to rest in a time interval \(\Delta t\). In Test 2, a different car of mass \(2M\) traveling at speed \(3v\) is brought to rest in a time interval \(4\Delta t\). If the average net force exerted on the car during Test 1 is \(F_1\) and the average net force exerted on the car during Test 2 is \(F_2\), what is the ratio \(F_2/F_1\)?