A body of weight 600N rests on the floor of a lift. If the lift begins to fall freely under gravity, what is the force with which the body presses on the floor?

When the lift is falling freely under gravity, then the body of weight 600N kept in it also falls freely under the action of gravity. In this case the reaction (force) of the floor of the lift, on the body is, zero. So the action (force) of the body on the floor of the lift should also be zero. Thus, the body on the floor of the lift exerts no force when the lift is falling freely under gravity. The body is "weightless" under these conditions.