how should i interpred the mass?

For example: i have a ship on water, the ship weights 10000kg.

and the mainengine has a power of 100kg.

but if i setting a mass of 10000 to the ship and applying a force of 100 nothing happens.

how do i restrict the direction of an objct?

and how to restrict rotation about an Axis?

the object should stay on the ground and move only about the y (UNIT_Y) axis.

Mass is in kg. If you want to be able to move your ship say across some ground you have to lower the grounds friction to make this ship “slide” across the floor like a ship does on the sea.