Atoms can exist on their own or as molecules. Forces are responsible for changing the motion of objects. If more than one force is present, the shape of an object can also be changed. Momentum ...

to the left and one with a force of 4 newtons (N) to the right, the combined effect of the two forces is to pull the trailer to the right with a resultant force of 4 – 3 = 1 newton (N).