First find the mass. Since weight force is 48N, and acceleration due to gravity is 9.8 m/s^2, weight force = mass*acceleration due to gravity, mass = weight/acceleration mass = 48N / 9.8 m/s^2 mass = 4.9 kg
Now you find the force needed to accelerate to 3.0 m/s^2. Force = mass*acceleration Force = 4.9kg * 3.0 m/s^2 Force = 14.7 N