Average velocity of a car

Problem

A car covers a straight stretch of $450\;\mathrm{m}$ in $30\;\mathrm{s}$ at constant velocity. Calculate the average velocity.

Solution

The average velocity is defined as the ratio between the displacement and the time interval taken to cover it:

$\bar{v} = \frac{\Delta s}{\Delta t}$

Substituting the problem’s data:

$\bar{v} = \frac{450\;\mathrm{m}}{30\;\mathrm{s}} = 15\;\mathrm{m/s}$

Since the motion happens at constant velocity, in this case the average velocity coincides with the instantaneous velocity at every point of the path. In kilometres per hour this is $15 \cdot 3{,}6 = 54\;\mathrm{km/h}$.

$\ev{\bar{v} = 15\;\mathrm{m/s}}$

Links

Topics: Cinematica Concepts: Velocità media