Question

A car starts from rest and attains the speed of $1km/hr$ and $2kms/hr$ at the end of $1st$ and $2nd$ minutes. If the car moves on a straight road, the distance travelled in $2$ minutes is

• A. $\frac{1}{20}km$
• B. $\frac{1}{30}km$
• C. $15km$
• D. $20km$

Answer 1

Answer: (A)

$\frac{1}{20}km$

$s_1=vt=\frac{1}{60}$

$v=at=\frac{1}{60}$

$v^2=u^2+2as$

${\left(\frac{2}{60}\right)}^2={\left(\frac{1}{60}\right)}^2+2\times a\times s_2$

$\frac{4-1}{{60}^2}=\frac{1}{30}{s}_2\Rightarrow s_2=\frac{1}{40}$

$s=s_1+s_2=\frac{1}{120}+\frac{1}{40}=\frac{4}{120}=\frac{1}{30}km$