Which of the diagrams in the figure correctly shows the change in kinetic energy of an iron sphere falling freely in a lake with sufficient density to impart it a terminal velocity?

1.   2.
3. 4.
(b) Hint: Apply the concept of work-energy theorem.
the First velæity of the iron sphere increases and after sometime constant called terminal velocity. Hence, accordingly, first KE increases and then becomes constant which is best represented by (b).