Answer:
180 [J].
Explanation:
1) the required work [W] can be calculated as difference of the energy: W=E₂-E₁, where E₁=mgh₁ - the energy before lifting, E₂=mgh₂ - the energy after lifting;
2) W=mgh₂-mgh₁, where m - mass; g=10 [N/kg], h - height;
3) then the required work [W]:
W=mg*(h₂-h₁)=30*6=180 [J].
