Question

A body starts from rest and moves with an acceleration Of 4m/s^2. (A) in what time will the body acquire a speed of 80m/s? (B) how much distance will it travel in this time?

Answer 1

$$\begin{gathered} \left(\mathrm{a}\right) \\ \mathrm{Final}\mathrm{velocity}: \\ \mathrm{v}=\mathrm{u}+\mathrm{at} \\ \mathrm{Hence}, \\ \mathrm{Time},\mathrm{t}=\frac{\mathrm{v}-\mathrm{u}}{\mathrm{a}} \\ =\frac{80-0}{4} \\ =20\mathrm{s} \\ \left(\mathrm{b}\right) \\ \mathrm{Distance}\mathrm{travelled}: \\ \mathrm{s}=\frac{\mathrm{u}+\mathrm{v}}{2}\times \mathrm{t} \\ =\frac{0+80}{2}\times 20 \\ =800\mathrm{m} \end{gathered}$$