Question

I need a formula to help understand how to get the answer?

Answer 1

From the table:

When time;

$t_1=0\text{ s}$

The position;

$x_1=20\text{ m}$

And when time,

$t_2=4\text{ s}$

The position;

$x_2=40\text{ m}$

The average velocity is given as,

$\begin{gathered} v_{av}=\frac{\text{ total displacement}}{\text{ total time taken}} \\ =\frac{x_2-x_1}{t_2-t_1} \end{gathered}$

Substituting all known values,

$\begin{gathered} v_{av}=\frac{(40\text{ m})-(20\text{ m})}{(4\text{ s})-(0\text{ s})} \\ =5\text{ m/s} \end{gathered}$

Therefore, the average velocity at t=4 s is 5 m/s.