An object is moving with variable speed,then

$A$ particle moves along $X$-axis in such a way that its coordinate $x$ varies with time $t$ according to the equation $x = (2 - 5t + 6t^2) \ m$. The initial velocity of the particle is ....... $m/s$.

The distance travelled by an object in time $t$ is given by $s = 2.5 t^2$. The instantaneous speed of the object at $t = 5\,s$ will be $....\,m/s$.

The figure shows a velocity-time graph of a particle moving along a straight line. The correct displacement-time graph of the particle is shown as:

Figures $(i)$ and $(ii)$ below show the displacement-time graphs of two particles moving along the x-axis. We can say that

What does $\dot x$ represent?