Question -
Answer -
( a ) Let us consideran example of a football, it is passed to player B by player A and theninstantly kicked back to player A along the same path. Now, the magnitude ofdisplacement of the ball is 0 because it has returned to its initial position.However, the total length of the path covered by the ball = AB +BA = 2AB. Hence,it is clear that the first quantity is greater than the second.
( b ) Taking the aboveexample, let us assume that football takes t seconds to cover the totaldistance. Then,
The magnitude of theaverage velocity of the ball over time interval t = Magnitude ofdisplacement/time interval
= 0 / t = 0.
The average speed ofthe ball over the same interval = total length of the path/time interval
= 2AB/t
Thus, the secondquantity is greater than the first.
The above quantitiesare equal if the ball moves only in one direction from one player to another(considering one-dimensional motion).