Ab object at rest will remain at rest unless acted by an unbalanced force, an object in motion will remain in motion in a straight line and A constant speed unless acted on by an unbalanced force.
Force = Mass time times acceleration. In other words, the greater a mass the greater the force required to that mass. To stop moving mass the greater the mass, the greater the force required to stop it.
For every action there is an equal and opposite reaction. It means that when two objects interact there are a pair of forces interacting on the two objects, in opposite directions.