Which of the following is one dimensional motion:

In the cube of side $a$ shown in the figure, the vector from the central point of the face $ABOD$ to the central point of the face $BEFO$ will be:

When a particle moves with variable velocity, which of the following statement are NOT correct ?
(i) Average speed = average velocity
(ii) Instantaneous speed = instantaneous velocity
(iii) Distance covered = magnitude of displacement

A particle is moved in a semi-circular path of radius $\mathrm{R}$. Then

Two skaters, $P$ and $Q$ are skating towards each other. Skater, $P$ throws a ball towards, $Q$ every $5 \mathrm{s}$ such that it always leaves her hand with speed $2 \mathrm{m} {\mathrm{s}}^{-1}$ with respect to the ground. Consider two cases: (I) $P$ runs with speed $1 \mathrm{m} {\mathrm{s}}^{-1}$ towards $Q,$ while $Q$ remains stationary. (II) $Q$ runs with speed $1 \mathrm{m} {\mathrm{s}}^{-1}$ towards $P,$ while $P$ remains stationary. Note That irrespective of speed of $P,$ ball always leaves $P$ s hand with speed $2 \mathrm{m} {\mathrm{s}}^{-1}$ with respect to the ground. Ignore gravity. Balls will be received by $Q.$