Dave who has a mass of 66kg stands motionless on a force pla

Dave, who has a mass of 66kg, stands motionless on a force plate then initiates a counter-movement vertical jump. At the instant he starts the counter movement, his vertical ground reaction force decreases to 337N and remains constant for 0.14s. His vertical ground reaction force then increases to 2427N and remains constant for 0.11s at which time he left the ground. What was his vertical velocity at the instant he left the ground?

Solution

from Newton\'s second law ,we have\":

           F1dt1 - f dt2 = mv

           mv = 2427* 0.11 - 337* 0.14

           mv = 219.79

hence, the velocity is,

      v =219.79 /66 = 3.33 m/s