Pulley question about a mass on a string

i'm having a lot of trouble with this question.
A pulley, consisting of a 0.40 m diameter wheel mounted on a horizontal frictionless axle, is firmly attached to the ceiling. A light rope wrapped around the pulley supports a 0.50 kg object, as shown in the diagram below. Any motion of the rope causes the pulley to turn, with no slipping between the rope and pulley. When released from rest, the object accelerates downward at 5.0 m/s2.

1) find the tension in the rope.
2) the torque on the pulley from the rope
3) the angular acceleration of the pulley
4) the moment of inertia of the pulley.

I'm stuck on the first part i keep getting 2.5N since the tension = ma it should be T=5m/s^2 * 0.5 kg but the answers say 2.4N and I can't figure out why. im assuming it has something to do with the pulley but since it is frictionless i dont see how it adds tension.

Consider the hanging mass only. There are two forces acting on it, gravity and the rope.
F = m a
Fg - Tension = 0.50 x 5
m x g - Tension = 2.5
0.5 x 9.8 - T = 2.5
4.9 - T = 2.5
T = 2.5 - 4.9
T = 2.4N