Twinkle throws a stone of mass 1 kg in vertically upward direction. Its velocity continuously decreases. After attaining a certain height its velocity becomes zero and it starts falling towards earth under gravitational force. If the acceleration due to gravity working on it is10 m/sec2. Then, how much force will it exert on ground, when it will strike to the ground?

• A. 10 N               
• B.          20 N
• C. N                    
• D. 100 N