A particle is constrained to move on a straight line path. It returns to the starting point after $10\, sec$. The total distance covered by the particle during this time is $30\, m$. Which of the following statements about the motion of the particle is false

The speed-time graph of a particle moving along a fixed direction is shown in Figure 

$(a)\; t = 0\; s$ to $10 \;s$, $(b)\;t=2 \;s$ to $6\; s$

What is the average speed of the particle over the intervals in $(a)$ and $(b)$?

A car travels from $A$ to $ B $ at a speed of $20\,\,km/hr$ and returns at a speed of $30\,\,km/hr$. The average speed of the car for the whole journey is............$km/hr$

A car goes from $A$ to $B$ (without changing direction), during first part of journey its average speed is $V_1$ and for second part of journey average speed is $V_2$ . The ratio path length of second part to the path length of first part is $\sqrt {\frac{{{V_2}}}{{{V_1}}}} $ . In that case the average speed of total path is ....... of average speeds of both parts. Choose correct option of fill. 

A boy walks to his school at a distance of $6\, km$ with constant speed of $2.5\, km/hour $ and walks back with a constant speed of $4 \,km/hr.$ His average speed for round trip expressed in $km/hour$, is

If the body covers one-third distance at speed $v_1$, next one third at speed $v_2$ and last one third at speed $v_3$, then average speed will be