Question

when u and v are there and a is uniform what is the formula for avg speed

Answer 1

this is Wright answer

Answer 2

Keep in mind that this works only when vu>0.$\text{From First equation of motion,}\\v=u+at\\\Rightarrow at=v-u\\\text{Put this into second equation of motion,}\\s=ut+\frac{1}{2}at^2\\s=ut+\frac{1}{2}(v-u)t\\\text{Divide both sides by t}\\<v>=\frac{s}{t}=u+\frac{1}{2}(v-u)\\=\frac{v+u}{2}$