Physics - Kinematics Question with Solution | TestHub

According to question,

Object$\mathrm{P}$starts at$\mathrm{t}=0$and acceleration of$\mathrm{P}=40\mathrm{ }\mathrm{k}\mathrm{m}/{\mathrm{h}}^2$

The time taken by object$\mathrm{P}$to cover$\mathrm{20 }\mathrm{k}\mathrm{m}$will be,

$\mathrm{s}=\mathrm{ut}+\frac{1}{2}{\mathrm{at}}^2$

Where,$\mathrm{u}=0,\mathrm{ }\mathrm{s}=\frac{1}{2}{\mathrm{at}}^2$

$\mathrm{t}=\sqrt{\frac{2\mathrm{s}}{\mathrm{a}}}$

Here,$\mathrm{a}=40\mathrm{ }\mathrm{k}\mathrm{m}/{\mathrm{h}}^2$

and$\mathrm{s}=20 \mathrm{k}\mathrm{m}$

$\mathrm{t}=\sqrt{\frac{2\mathrm{ }\times \mathrm{ }20}{40}}$

$=1 \mathrm{hour}$

Time taken by$\mathrm{Q}$will be$\frac{1}{2} \mathrm{hour}$, because it started after$30 \min$.

The acceleration in$\mathrm{Q}$,

$\mathrm{a}=\frac{2\mathrm{s}}{{\mathrm{t}}^2}=\frac{2\mathrm{ }\times \mathrm{ }20}{{\left(\frac{1}{2}\right)}^2}$

$=2\times 4\times 20$

$=160 \mathrm{k}\mathrm{m}/{\mathrm{h}}^2$