we are asked in the problem to determine the horizontal distance achieved by rolling of a pen from a vertical distance of 0.55 m at 1.2 m/s.
we use the formula in this case,
t = √[2y/g]
where g is the gravitational acceleration
t = √[2*0.55/9.8] =0.335 s
X = v * t = 1.2 m/s *0.335 s = 0.4 m