A block is placed on an elevator platform that moves downward with decreasing speed. Consider the time interval t₀ , in which the speed of the platform changes from v₀ to zero. (a) Sketch a free-body diagram for the block.

(b) Is the net work done on the block positive, negative, or zero?

(c) For each force on the free-body diagram, state whether the work done on the block by that force is positive, negative, or zero. Explain.

(d) Rank the works you identified above in order of decreasing absolute value. Explain.

(e) Is the change in kinetic energy of the block positive, negative, or zero?