Ta có: \(m=50kg\Rightarrow t=10s\)
\(m+m'=50+m'\Rightarrow t'=20s\)
\(------\)
\(s=\frac{1}{2}at^2=\frac{1}{2}a.10^2=50a\)
\(s=\frac{1}{2}a't'^2=\frac{1}{2}a'.20^2=200a'\)
\(\Rightarrow50a=200a'\)
\(\Rightarrow a=4a'\)
\(F=ma\)
\(F=\left(m+m'\right)a'\)
\(\Rightarrow ma=\left(m+m'\right)a'\)
\(50.4a'=\left(50+m'\right)a'\)
\(m'=150kg\)
Vậy ...................