Question

A car is moving with a velocity of $90\text{km/h}$. The application of brakes offers a constant retardation of $5{\text{m/s}}^2$. Find the distance travelled by the car before it comes to rest.

• A. $50\text{m}$
• B. $62.5\text{m}$
• C. $625\text{m}$
• D. $125\text{m}$

Answer 1

The correct option is B $62.5\text{m}$

Initial speed $=90\text{km/h}=25\text{m/s}$, acceleration $=-5{\text{m/s}}^2$
Using the third equation of motion,
$v^2-u^2=2as$
We have, $(0{)}^2-(25{)}^2=2(-5)\text{s}$
$s=62.5\text{m}$