Pseudo Force Questions

A person is standing in an elevator. In which situation he finds his weight less?

A block of mass $m$ is in contact with the cart $C$ as shown in the figure. The coefficient of static friction between the block and the cart is $\mu$. The acceleration $\alpha$ of the cart that will prevent the block from falling satisfies:

A balloon with mass ‘m’ is descending down with an acceleration ‘a’ (where $a<g$). How much mass should be removed from it so that it starts moving up with an acceleration ‘a’?