Friction. Since "air" is not a vacuum, it takes energy to move through it in the same way it takes energy to move through water. (though this is a more drastic example.) If there is no active energy source to keep an object pushing past the particles in the air (like a propeller or rocket) it will slow down as it loses momentum.
friction stops things from moving and slows it down
straight
friction is the force that slows things down or prevent things from moving
the force is called gravity (I'm not really sure if that's the right answer, but you can just go to google and type in force that slows down moving objects, glad if I helped(:
Presumably you mean friction.
friction stops things from moving and slows it down
Whenever another force - usually friction - slows it down.
friction
friction
straight
friction is the force that slows things down or prevent things from moving
Friction
Friction?
the force is called gravity (I'm not really sure if that's the right answer, but you can just go to google and type in force that slows down moving objects, glad if I helped(:
Presumably you mean friction.
Friction slows down moving objects and brings it to a stop unless there is an stronger opposing force
friction