Seagull is at height 11 m
it drops a shell from rest
so here we know that
acceleration of shell is due to free fall = -9.81 m/s^2
displacement = - 11 m
initial speed = 0
now we will use kinematics equation here in order to find the final speed

now plug in all values in it



so here the speed by which shell will strike with the rocks is 14.7 m/s