Question

If a particle is moving from its initial position $x=-5\text{m}$ to a position $x=-11\text{m}$ in $2\text{s}$ along a straight line. What will be the average velocity of particle ?

• A. $5\text{m/s}$
• B. $-3\text{m/s}$
• C. $3\text{m/s}$
• D. $-6\text{m/s}$

Answer 1

The correct option is B $-3\text{m/s}$

Displacement is the difference of final and initial position.
$\Rightarrow \Delta x=x_f-x_i$
$\Rightarrow \Delta x=-11-(-5)=-6\text{m}$
Hence average velocity is,
${\text{Velocity}}_{\text{avg}}=\frac{\Delta x}{\Delta t}$
$\Rightarrow {\text{Velocity}}_{\text{avg}}=\frac{-6}{2}$
$\therefore {\text{Velocity}}_{\text{avg}}=-3\text{m/s}$
The negative sign of average velocity indicates that particle is moving along $-vex-$axis.