The distance travelled by a motor car in t seconds after the brakes are applied is s feet, where $s=22 t-12 t^2$. The distance travelled by the car before it stops, is
Answer & explanation
Correct answer: option 1
We have,
$s=22 t-12 t^2 \Rightarrow \frac{d s}{d t}=22-24 t$
When the car stops, $\frac{d s}{d t}=0$
∴ $22-24 t=0 \Rightarrow t=\frac{11}{22}$
∴ $s=22 t-12 t^2 \Rightarrow s=22 \times \frac{11}{22}-12 \times\left(\frac{11}{22}\right)^2$ = 10.08 ft