<-- These 4 transportations uses density because: To
make an object or aircraft float in the water or the in
the air, the object's density has to be less densed than
the air/water it self. (SAME REVERSED)
If the air or water molecule is densed, the object that
you want to make it float has to be less densed, so it
floats.
4 Forms of Transportation That Uses DENSITY:
1) BOATs
2) HOT AIR BALLOONs
3) HELICOPTER
4) PLANES
For HOT AIR BALLOON: Heat makes the
object have less density and makes the
balloon float.