Cách 1:
Ta có:
`v^2-v_0^2=2as`
`<=> (v_0+at)^2-v_0^2=2as`
`<=> v_0+at=\sqrt{2as+v_0^2}`
`=> t=\frac{\sqrt{2as+v_0^2}-v_0}{a}`
Cách 2:
Ta có:
`s=v_0t+\frac{1}{2}at^2`
`<=> s=v_0.\frac{v-v_0}{a}+\frac{1}{2}at^2`
`<=> 2.(s-v_0.\frac{v-v_0}{a})=at^2`
`=> t=\sqrt{\frac{2(s-v_0.\frac{v-v_0}{a})}{a}}`