The displacement of an object or particle is defined as its change in position, from point A to point B. 
                                                                   

Instantaneous velocity (or just velocity) is defined as the rate of change of the particle's position x, or dx/dt.  Velocity is a Vector quantity. 

                                                                  

Speed is the magnitude of velocity and it is a Scalar with no assigned direction. 
                                                                  

Instantaneous acceleration (or just acceleration) is the time derivative (dv/dt or d²x/dt) of velocity or the rate of change of the velocity. For more on speed and acceleration visit: http://www.gcse.com/fm/sdt.htm              

A force does work on a body when the body undergoes a displacement in the direction of the force. Work is a scalar quantity, and it is determined by integrating the dot product of the force and the finite displacement element.  For more about work visit: http://cpphysics.homestead.com/energyt.html.

                                                                 

Power is the amount of work performed per unit time, which is the time derivative of work. Power is a scalar quantity. 
                                                                

A force is conservative if the work done by the force on a body is independent of the path followed by the body.  Weight is a conservative force. 
                                                               

Potential energy is the measure of the amount of work a conservative force will do on an object when moving it from a certain position to another position. 
                                                               

Kinetic energy is defined as energy in motion. 
                                                               

Impact occurs when two bodies collide with each other during a very short period of time, and cause relatively large forces to be exerted between the bodies.