Which of these is a correct distance-time graph for the motion of the body?
Let's analyze the motion of the body.
(1) Body is moving in 1 dimension. Lets take X axis of the given graph from t = 0 t=tb :the particle goes from starting point to point B, 10 m away.
till t = tb
Now till t = displacement is costant i.e. the particle didn't move from the place.
Till t = tc
So distance time graph will be like
Now till t = 20 sec body comes back to origin or the starting point so the distance travelled by the particle will increase though its displacement has decreased.
Now distance travelled is 20 m.
Now in time duration t = 20 to t = 30 the particle is going in opposite direction so -ve displacement but still the particle is moving so distance travelled will keep on increasing.