A vehicle travels half the distance with speed $$v$$ and the remaining distance with speed $$2 v$$. Its average speed is :

The position-time (x - t) graph for positive acceleration is

The ratio of the distances travelled by a freely falling body in the 1^st, 2^nd, 3^rd and 4^th second

The displacement-time graphs of two moving particles make angles of 30$$^\circ$$ and 45$$^\circ$$ with the x-axis as shown in the figure. The ratio of their respective velocity is