grad Displacement vector is the change in the position vector.

Acceleration and instantaneous velocity may have opposite directions.

The equation $v^2=2ad$ is dimensionally correct $(v,a,d$ have the usual meaning$).$

The difference of two non$-$zero vectors may have the same magnitude as their sum.

The difference of two non$-$zero vectors may have the same direction as their sum.

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To calculate the weight of an object $($in newtons$),$ we multiply its mass $($in kilograms$)$ by $-9\mathrm{.}81\frac{m}{s^2}.$

The sum of two non$-$zero vectors may be zero.