Question

starting from rest an aeroplane takes off after travelling a distance of 0.7 km on the runway.it takes of at 35 m/s calculate time for which it moves on the runway

Answer 1

Dear Student,

$$\begin{gathered} \mathrm{distance},\mathrm{s}=0.7\mathrm{km}=700\mathrm{m} \\ \mathrm{initial}\mathrm{velocity},\mathrm{u}=0 \\ \mathrm{final}\mathrm{velocity},\mathrm{v}=35\mathrm{m}/\mathrm{s} \\ {\mathrm{v}}^2-{\mathrm{u}}^2=2\mathrm{as} \\ {\left(35\right)}^2-0^2=2\times \mathrm{a}\times 700 \\ \mathrm{a}=\frac{1225}{1400}=0.875\mathrm{m}/{\mathrm{s}}^2 \\ \mathrm{Also},\mathrm{v}=\mathrm{u}+\mathrm{at} \\ 35=0+0.875\mathrm{t} \\ \mathrm{t}=\frac{35}{0.875}=40\mathrm{s} \end{gathered}$$