Question

A motorcar is moving with a velocity of $108km/h$ and it takes $4s$ to stop after the brakes are applied. Calculate the force exerted by the brakes on the motorcar if its mass along with the passengers is $1000kg.$

Answer 1

Force=mass*acceleration

$f=m\times \frac{v-u}{t}$

$f=1000\times \frac{0-108\times \frac{5}{18}}{4}$

$=1000\times (-7.5)$

$\therefore f=-7500N$

opposing force is denoted by negative sign.