Question

A stone thrown from ground level returns to the same level 4s after. With what speed was the stone thrown? Take g = 10m/s^2

Answer 1

\[x_{f}=x_{i}+v_{i}+12(a) (t^2) \rightarrow 4s(v_{i})−80m/s^2 \rightarrow v_{i}=20m/s\]