Answer:
v = 6.93 m/s
Step-by-step explanation:
given,
spring constant = k = 400 N/m
compression of spring = 6 cm = 0.06 m
mass of ball = 0.03 Kg
length of barrel = 6 cm
using energy conservation
KE of ball = PE of spring





v = 6.93 m/s
hence, the speed at which ball leaves the barrel will be equal to v = 6.93 m/s