AL PHY Mechanics- S.H.M

The answer is option A. Between A and B, the gymnast is in contact with the elastic sheet.

Option B is correct, because OA and EF represents the velocity during the time intervals when the gymnast is falling down and going out under gravity respectively. The slope represents the acceleration due to gravity, which is a constant of about 10 m/s2.

Option C is correct, point C is the time when the gymnast starts to rebound, as the velocity changes from +ve (downward direction) to -ve (upward direction). At this moment, the elastic sheet deforms most.

Option D is correct. The areas represents the displacement of the gymnast. As said above, point C is the point of rebound from the lowest position. Hence, area I represents the displacement from the highest position (point O) in air to the lowest position at C. Areas II represents the displacement from the lowest position to the highest position in air (point F).