Choose the correct relation from the following for any motion in space

• A

  ${\overrightarrow{\mathrm{v}}}_{\text{average }}=\frac{1}{2}\left[\overrightarrow{\mathrm{v}}\left({\mathrm{t}}_1\right)+\overrightarrow{\mathrm{v}}\left({\mathrm{t}}_2\right)\right]$

• B

  ${\overrightarrow{\mathrm{v}}}_{\text{average }}=\frac{\overrightarrow{\mathrm{r}}\left({\mathrm{t}}_2\right)-\overrightarrow{\mathrm{r}}\left({\mathrm{t}}_1\right)}{{\mathrm{t}}_2-{\mathrm{t}}_1}$

• C

  $\overrightarrow{v}\left(t\right)=\overrightarrow{v}\left(0\right)+\overrightarrow{a}t$

• D

  $\overrightarrow{r}\left(t\right)=\overrightarrow{r}\left(0\right)+\overrightarrow{v}\left(0\right)t+\frac{1}{2}\overrightarrow{a}{t}^2$

  (The average stands for average of the quantity over the time interval t₁ to t₂)