Path Length ( Distance ) Vs . Displacement
Path Length : It is the distance between two points along a straight line . It is scalar quantity .
Displacement : It is the change in position in a particular time interval . It is vector quantity . Change is position is usually denoted by Δx ( x2-x1 ) and change in time is denoted by Δt ( t2-t1 ).
For the above example , if a person goes from home ( O ) to school ( x2 ) and comes back from school to Park ( x1 ), then
Path length ( Home to School and School to Park ) = Ox2 + x2x1 = (+ 80 ) + (+ 60 ) = + 140m . This is always positive .
Displacement ( Home to Park ) = Ox2 - x2x1 = + 80 – (+ 60 ) = + 20m . This can be positive as well as negative . The negative sign indicates the direction .
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Magnitude of Displacement may or may not be equal to the path length .
For a non-zero path length , displacement can be 0 ( case where an object returns to origin ).