The figure shows the velocity $(v)$ of a particle plotted against time $(t)$.

State whether the following statements are true or false:
$(a)$ An object can have acceleration even when its velocity is zero.
$(b)$ If the acceleration of a moving object is constant,the direction of its velocity must remain the same.
$(c)$ The speed of an object can never be zero.

$A$ particle starts from rest,accelerates at $2 \, m/s^2$ for $10 \, s$,then moves at a constant speed for $30 \, s$,and finally decelerates at $4 \, m/s^2$ until it stops. What is the total distance travelled by it in $m$?

The driver of a bus moving with a velocity of $72 \ km/h$ observes a boy walking across the road at a distance of $50 \ m$ in front of the bus and decelerates the bus at $5 \ m/s^2$ by applying brakes and is just able to avoid an accident. The reaction time of the driver is (in $s$)

$A$ particle moves along the sides $AB, BC, CD$ of a square of side $25 \, m$ with a constant velocity of $15 \, m \, s^{-1}$. Its average velocity is ........ $m \, s^{-1}$.

$A$ bead is moving in medium $1$ with a uniform speed of $1\, m/s$ for $2.5\, s$. Then it enters into air and falls freely under gravity for $2\, m$. Finally, it enters medium $2$ and immediately moves with uniform speed for $1.5\, s$. The total distance the bead has traveled is.........$m$ $(g = 10\, m/s^2)$: (in $.1$)