What Is a Force?
A force is a push or a pull… it’s what makes something go–change speed, change direction, start when it’s stopped or stop when it’s going. Learn more about the basics of forces…
http://www.glenbrook.k12.il.us/gbssci/Phys/Class/energy/u5l1a.html
http://www.batesville.k12.in.us/physics/PhyNet/Mechanics/Newton1/what_is_a_force_really.htm