Acceleration from rest

Problem

A car starts from rest and reaches $v = 15\;\mathrm{m/s}$ in $6{,}0$ seconds. Calculate the average acceleration, assumed constant.

Solution

The average acceleration is the ratio between the change in speed and the time interval over which it occurs:

$\bar{a} = \frac{\Delta v}{\Delta t} = \frac{v - v_0}{\Delta t}$

The car starts from rest, so the initial speed is $v_0 = 0$. Substituting the data:

$\bar{a} = \frac{15\;\mathrm{m/s} - 0}{6{,}0\;\mathrm{s}} = 2{,}5\;\mathrm{m/s}^2$

The result means that every second the car’s speed increases by $2{,}5\;\mathrm{m/s}$.

$\ev{a = 2{,}5\;\mathrm{m/s}^2}$

Links

Topics: Cinematica Concepts: Accelerazione