In which motions are the distance and the displacement the same?

A. A dog chases its tail in a circle four times
B. A bird flies from its nest to the ground and back to its nest.
C. A worm moves 5 cm along a straight crack in a sidewalk.
D. A fish swims all the way across a pond and then halfway back.

A. A dog chases its tail in a circle four times.

Explanation:

Distance can be defined as a scalar quantity. It describes how much area the object covers during its motion. Displacement can be defined as the vector quantity. It refers to the fact that how far an object is from a place. It describes the overall change in the position of the object.

A dog makes a circle four times chasing the tail thus its direction will remain the same.  Its position will remain the same after motion, thus no displacement will occur.  The dog is making a circle on the same place while chasing the tail hence the distance covered will become equal to the net displacement.  

the rocks are classified by the geological process they are formed by. the three main groups of rocks are igneous, metamorphic, and sedimentary. minerals are not they are classified under the chemical classes they are in. these groups include silicates, sulfates and carbonates.

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