The train in question is big and heavy and a car is decently heavy but say a train moving at 55 mph can plow through a car and a car driving at 55mph driving at a train will be stopped dead in its tracks. This is because newtons laws of motion specifically an object in motion will stay in motion unless its opposed. The train also has a payload behind it meaning it hurts with force while a car doesn't have to much mass behind it. The train takes loner to stop for as it's acceleration as well as it's deceleration are very slow because its huge and takes a lot of force to stop it while a car is very centralized and compact when it comes to weight and its brakes are usually effective at stopping at 55 mph in about 2 to 6 seconds while a train might stay moving for a good 35 seconds. The force behind the train is immense for as even if the wheels don't spin at all the train will still move since the force behind it is great and a cars tires have a lot of grip and not a lot mass which plays into the force the car has so it can stop simply.
Answer: Rock candy is candy made of large sugar crystals. To make rock candy, a supersaturated solution of sugar in water is created and left undisturbed for a few days. The driving force behind crystallization is supersaturation.
The firefighter with an acceleration of 3m/s^2 take the gravity acceleration as 10m/s^2 isn't necessary to know the coefficient of friction just to know the force of friction:
