An 80kg athlete jumps up 1.5 meters. with what velocity does he hit the ground?

m = mass of the athlete = 80 kg

h = height from where the athlete drops = 1.5 meters

g = acceleration due to gravity = 9.8 m/s²

v = speed with which the athlete hit the ground = ?

as per conservation of energy, the sum of potential energy and kinetic energy remain same all the time. if one increase, the other decrease by same amount to keep the total energy same.

hence in this case, as the athlete drops, the potential energy decrease due to decrease in the height. to keep the total energy constant, the kinetic energy increase by same amount.

hence,

kinetic energy gained = potential energy lost

(0.5) m v² = mgh

dividing both side by mass "m"

(0.5) v² = gh

(0.5) v² = (9.8 x 1.5)

v = 5.42 m/s