6. A car of mass 1.25 tonnes tows a caravan of mass 0.75 tonnes along a straight, level road. The total resistance to motion experienced by the car and the caravan is 1200 N . The car and caravan accelerate uniformly from rest to \(25 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) in 20 seconds.

1. Calculate the driving force produced by the car's engine. Given that the resistance to motion experienced by the car and by the caravan are in the same ratio as their masses,
2. find these resistances and the tension in the towbar. When the car and caravan are travelling at a steady speed of \(25 \mathrm {~ms} ^ { - 1 }\), the towbar snaps. Assuming that the caravan experiences the same resistive force as before,
3. calculate the distance travelled by the caravan before it comes to rest,
4. give a reason why your answer to (c) may be unrealistic.