Question

A body which is uniformly retarded comes to rest in 10 seconds after travelling a distance of 20m. Calculate its initial velocity

Answer 1

The initial velocity can be found from the following kinematic equation (see https://www.khanacademy.org/science/physics/one-dimensional-motion/kinematic-formulas/a/what-are-the-kinematic-formulas):

$$d = \dfrac{v + v_0}{2}t$$

where $d = 20m$ is the distance, $v = 0m/s$ is the final speed, $v_0$ is the initial speed, and $t = 10s$ is the time. Expressing $v_0$, obtain:

$$v_0 = \dfrac{2d}{t} = \dfrac{2\cdot 20m}{10s} = 4m/s$$

Answer. 4m/s.