motiontranslationaverage speed Rotation kinematics center of mass Center of gravity gravitational force Gravity displacement direction Vector quantity speed velocity Raterelative motionacceleration Rotational motion

 Motion – is the change in position and orientation of an object.  Translational motion (translation) is the movement of a rigid object’s center of mass from one place to another.  Rotational motion (rotation) is the movement around a rigid object’s center of mass.

 Kinematics is the study of the motion of objects from one point to another. Insert satellite spinning diagram (1)

 Linear motion – is movement in a straight line and is the simplest form of translational motion.  The linear motion of any rigid object is described as the motion of its center of mass.

 Center of mass – the point which acts as though the total mass of the object were at that point.  The center of mass of a rigid object is in the same position as its center of gravity.  The center of gravity of an object is the point through which the Earth’s gravitational force acts on the object. Insert center of mass diagram (2)

 Displacement – is the distance and direction of an object from a fixed reference point.  It is a vector quantity.  The position of an object can be expressed by its displacement from a specified point. Insert displacement diagram (3)

 Speed is the ratio of the distance traveled by an object to the time taken.  If the speed of an object is constant, it is said to be moving with uniform speed.  The average speed of an object over a time interval is the distance traveled by the object divided by the time interval.  The instantaneous speed is the speed at any given moment. Insert speed diagram (4)

 Velocity is the speed and direction of an object (its displacement in a given time).  It is a vector quantity.  Uniform velocity, average velocity and instantaneous velocity are all defined in a similar way to uniform speed.

 Relative velocity is the velocity which an object appears to have when seen by an observer who may be moving.  This is known as the velocity of the object relative to the observer. Insert relative velocity diagram (5)

 Acceleration is the ratio of the change in velocity of an object to the time taken.  It is a vector quantity.  An object accelerates if its speed changes or its direction of travel changes.  Deceleration in one direction is acceleration in the opposite direction  (negative acceleration).

 An object whose velocity is changing the same amount in equal amounts of time is moving with uniform acceleration. Insert Graphs of velocity time graphs (6)

 Rotational motion is the movement of an object about its center of mass.  In rotational motion, each part of the object moves along a different path.  It must be split into small pieces and the circular motion of each piece must be considered separately. Insert rotational motion diagram (7)

 A sign convention is a method used to distinguish between motion in opposite directions.  The sign convention must be used when using the equations of motion because the equations use displacement not distance, so changes of direction must be considered. Insert sign convention diagram (8)