A lift is moving down with an acceleration a. A man in the lift drops a ball inside the lift. The acceleration of the ball as observed by the man in the lift, and a man standing stationary on the ground are, respectively, :

a, g (g - a), g a, a g, g

(g - a), g

\(\vec{a}_{b,l} = \vec{a}_b - \vec{a}_l\)   = \((g - a) \downarrow\)    \(\Rightarrow \vec{a}_b = g \downarrow\)