$A$ body falls freely for $10 \ s$. What is its average velocity during this journey (in $m/s$)? (Take $g = 10 \ m/s^2$)

When a ruler falls vertically, $5$ different persons catch it with different reaction times. $(g = 9.8 \text{ ms}^{-2})$
$A$. Person $A$ has reaction time of $0.20 \text{ s}$
$B$. Person $B$ has reaction time of $0.22 \text{ s}$
$C$. Person $C$ has reaction time of $0.18 \text{ s}$
$D$. Person $D$ has reaction time of $0.19 \text{ s}$
$E$. Person $E$ has reaction time of $0.21 \text{ s}$
What is the correct order of the distance travelled by the ruler for each person?

Can a particle moving in a straight line have zero velocity and non-zero acceleration at any instant? Give an example.

$A$ ball projected vertically upwards with a velocity '$v$' passes through a point $P$ in its upward journey in a time of '$x$' seconds. From there,the time in which the ball again passes through the same point $P$ is

The ratio of the distances travelled by a freely falling body in the $1^{\text{st}}$,$2^{\text{nd}}$,$3^{\text{rd}}$,and $4^{\text{th}}$ second is:

$A$ ball projected up passes the same height $H$ at $2 \,s$ and $10 \,s$. The value of $H$ is [Use $g=9.8 \,m/s^2$]. (in $m$)