http://img258.echo.cx/img258/4409/lift3ad.png A painter in a crate hangs alongside a building. When the painter, who weighs 1000 N, pulls on the rope, the force he exerts on the floor of the crate is 450 N. If the crate weighs 250 N, find the acceleration. (ans=1.96 m/s²) Lift accelerates upwards, because man is pulling down. hence, N (upwards) - mg (downwards) = ma (upwards) Is it right? Question: for mg and ma, do I need to take into account the mass of the crate?