A force is a push or a pull or a twist. 

Forces have both magnitude (size) and direction. The SI unit for measuring foce is the newton (N). 

There are contact forces and non-contact forces. When you push a box along the floor, there is contact. Whan a magnet attracts and pulls an iron nail towards it, there is no contact at first. 

Forces can do the following things:

• A force can stop a moving object. 

• A force can accelerate or decelerate a moving object. 

• A force can change the direction of motion of a moving object. 

• A force can change the shape of an object. 

• A force can keep an object in place. 

• A stationary object starts moving when a force acts on it. 

If a force pushes an object to the right and another force of the same magnitude (size) pushes it to the left, these two forces will cancel each other out and we say the forces are balanced. The net force or the resultant force will be zero and the object will remain stationary. When balanced forces act on a moving objec,