Question

An auto's velocity increase uniformly form 7.4 m/s to 20 m/s while covering 70m in straight line. Find the acceleration and the time taken.

Answer 1

We can find the acceleration of the car as follows:

$$v^2=v_0^2+2ad,$$ $$a=\dfrac{v^2-v_0^2}{2d},$$ $$a=\dfrac{(20\ \dfrac{m}{s})^2-(7.4\ \dfrac{m}{s})^2}{2\times70\ m}=2.47\ \dfrac{m}{s^2}.$$

We can find the time taken as follows:

$$v=v_0+at,$$ $$t=\dfrac{v-v_0}{a}=\dfrac{20\ \dfrac{m}{s}-7.4\ \dfrac{m}{s}}{2.47\ \dfrac{m}{s^2}}=5.1\ s.$$