We need to show that car A is safer than car B and this is done by showing that the force is greater on car B than car A.
Start by finding the force on car A, total mass 1580kg:
Force is the change of momentum / the time for which it acts.
Momentum before the crash = mv = 1580 x 20 = 31600kgm/s.
Momentum after = 0 as v = 0.
force = 31600/0.8 = 39500N (2)
Repeat this for car B and compare the results:
momentum before and after is the same
force = 31600/0.2 = 158000kgm/s (1)
Finally, to answer the question, finish with a closing statement such as: 'Car A has crumple zones which increase the collision time, this significantly reduces the force on the driver and makes the car much safer. Therefore crumple zones should be made a legal requirement' (3)