54J
You calculate kinetic energy by the equation.
KE= 1/2mv^2
m= mass
v= velocity
then we have
KE = 1/2 x 3 x 6^2
KE = 1/2 x 3 x 36 = 54J
Answer
given,
mass of ice hockey player = 110 Kg
initial speed of the skate = 3 m/s
final speed of the skate = 0 m/s
distance of the center of mass, m = 30 cm = 0.3 m
a) Change in kinetic energy



b) Average force must he exerted on the railing
using work energy theorem
W = Δ KE
F .d = -495
F x 0.3 = -495
F = -1650 N
the average force exerted on the railing is equal to 1650 N.